Fix #12: add xml2js options

[foobar98]

Fixes #12

As part of the parse options, consumers can now pass xml2js options in the object which was previously hardcoded.

options: {
  filePath: ..,
  xmlContent: ..,
  xmlOptions: ..
}

If not provided, it will default to -

var XML2JS_OPTS = {
  trim: true,
  normalizeTags: true,
  normalize: true,
  mergeAttrs: true
};

Signed-off-by: pgupta19 [email protected]