Support `res.setEncoding` and non-text response types

[wmrowan]

Response data in http-browserify seems to default to text. In node http it seems to default to buffer. Independent of defaults, the node version supports setEncoding so you can change the type of the response. The browserify version should do the same.

[Jxck]

+1 or support only setEncoding('utf8') and ignore others seems fine.

[tellnes]

See #10

[MiguelCastillo]

So, is there a plan to merge the PR?

[jamestalmage]

Would there be any value to throwing or at least logging an error if it is not utf-8?

+1 either way.

[jstoeffler]

+1

[drawm]

+1 Causes problem on other library. https://github.com/baalexander/node-xmlrpc/issues/135