Fix current linter issues

[daemonfire300]

Running make lint throws a lot of warnings. We probably want to fix/address them.

$ make lint
/Users/juliusfoitzik/go/bin/golangci-lint run
maintenance/log/handler.go:88:5: `noXid` is unused (deadcode)
var noXid = errors.New("no xid")
    ^
http/jsonapi/generator/generate_helper.go:16:7: `pkgRuntime` is unused (deadcode)
const pkgRuntime = "github.com/pace/bricks/http/jsonapi/runtime"
      ^
http/jsonapi/errors_test.go:53:18: Error return value of `json.Unmarshal` is not checked (errcheck)
			json.Unmarshal(buffer.Bytes(), &output)
			              ^
http/jsonapi/request.go:277:32: Error return value of `(*encoding/json.Encoder).Encode` is not checked (errcheck)
				json.NewEncoder(buf).Encode(data.Relationships[args[1]])
				                           ^
http/jsonapi/request.go:278:32: Error return value of `(*encoding/json.Decoder).Decode` is not checked (errcheck)
				json.NewDecoder(buf).Decode(relationship)
				                           ^
http/jsonapi/request.go:305:32: Error return value of `(*encoding/json.Encoder).Encode` is not checked (errcheck)
				json.NewEncoder(buf).Encode(
				                           ^
http/jsonapi/request.go:308:32: Error return value of `(*encoding/json.Decoder).Decode` is not checked (errcheck)
				json.NewDecoder(buf).Decode(relationship)
				                           ^
http/jsonapi/request_test.go:364:28: Error return value of `(*encoding/json.Encoder).Encode` is not checked (errcheck)
	json.NewEncoder(in).Encode(payload)
	                          ^
http/jsonapi/request_test.go:1097:16: Error return value of `MarshalPayload` is not checked (errcheck)
	MarshalPayload(out, testModel)
	              ^
http/jsonapi/request_test.go:1104:27: Error return value of `MarshalOnePayloadEmbedded` is not checked (errcheck)
	MarshalOnePayloadEmbedded(out, testModel())
	                         ^
http/jsonapi/request_test.go:1107:18: Error return value of `UnmarshalPayload` is not checked (errcheck)
	UnmarshalPayload(out, blog)
	                ^
http/jsonapi/response_test.go:30:16: Error return value of `MarshalPayload` is not checked (errcheck)
	MarshalPayload(out1, book)
	              ^
http/jsonapi/response_test.go:46:16: Error return value of `MarshalPayload` is not checked (errcheck)
	MarshalPayload(out2, books)
	              ^
http/jsonapi/runtime.go:83:18: Error return value of `r.instrumentCall` is not checked (errcheck)
	r.instrumentCall(UnmarshalStart, UnmarshalStop, func() error {
	                ^
maintenance/errors/raven/client.go:374:15: Error return value of `client.SetDSN` is not checked (errcheck)
	client.SetDSN(os.Getenv("SENTRY_DSN"))
	             ^
maintenance/errors/raven/client.go:956:9: Error return value of `io.Copy` is not checked (errcheck)
	io.Copy(ioutil.Discard, res.Body)
	       ^
maintenance/errors/raven/client.go:976:16: Error return value of `deflate.Write` is not checked (errcheck)
		deflate.Write(packetJSON)
		             ^
http/jsonapi/generator/generate_security.go:115:20: Error return value of `json.Unmarshal` is not checked (errcheck)
					json.Unmarshal(data, &url)
					              ^
http/transport/chainable_test.go:37:14: Error return value of `client.Get` is not checked (errcheck)
			client.Get(server.URL + "/test001")
			          ^
http/transport/chainable_test.go:42:13: Error return value of `client.Get` is not checked (errcheck)
		client.Get(server.URL + "/test002")
		          ^
http/transport/locale_round_tripper_test.go:35:15: Error return value of `lrt.RoundTrip` is not checked (errcheck)
	lrt.RoundTrip(r.WithContext(locale.WithLocale(context.Background(), l)))
	             ^
http/jsonapi/runtime/standart_params_test.go:100:14: Error return value of `db.DropTable` is not checked (errcheck)
	db.DropTable(&TestModel{}, &orm.DropTableOptions{
	            ^
maintenance/errors/raven/client.go:341:3: ineffectual assignment to `i` (ineffassign)
		i++
		^
http/jsonapi/runtime/standart_params_test.go:69:13: ineffectual assignment to `err` (ineffassign)
	urlParams, err = runtime.ReadURLQueryParameters(r, mapper, &testValueSanitizer{})
	           ^
http/jsonapi/runtime/standart_params_test.go:79:13: ineffectual assignment to `err` (ineffassign)
	urlParams, err = runtime.ReadURLQueryParameters(r, mapper, &testValueSanitizer{})
	           ^
http/jsonapi/runtime/standart_params_test.go:92:13: ineffectual assignment to `err` (ineffassign)
	urlParams, err = runtime.ReadURLQueryParameters(r, mapper, &testValueSanitizer{})
	           ^
maintenance/errors/raven/stacktrace.go:31:6: S1002: should omit comparison to bool constant, can be simplified to `frame.InApp` (gosimple)
		if frame.InApp == true && frame.Module != "" && frame.Function != "" {
		   ^
http/jsonapi/response_test.go:42:14: S1030: should use out1.String() instead of string(out1.Bytes()) (gosimple)
	fmt.Println(string(out1.Bytes()))
	            ^
http/longpoll/longpoll_test.go:17:41: S1024: should use time.Until instead of t.Sub(time.Now()) (gosimple)
		assert.Equal(t, time.Millisecond*999, budget.Sub(time.Now()).Truncate(time.Millisecond))
		                                      ^
http/longpoll/longpoll_test.go:29:35: S1024: should use time.Until instead of t.Sub(time.Now()) (gosimple)
		assert.Equal(t, time.Second*59, budget.Sub(time.Now()).Truncate(time.Second))
		                                ^
maintenance/errors/context_test.go:21:19: lostcancel: the cancel function returned by context.WithTimeout should be called, not discarded, to avoid a context leak (govet)
	exceededContext, _ := context.WithTimeout(backgroundContext, time.Millisecond)
	                 ^
http/jsonapi/runtime/error.go:119:4: SA4006: this value of `ev` is never used (staticcheck)
			ev = ev.Fields(*source)
			^
http/jsonapi/request_test.go:205:7: type `FooStruct` is unused (unused)
make: *** [lint] Error 1