Add full support of methods defined in RFC2616 and RFC5789 as per RAML spec

  * update raml-grammar
  * update raml-js-parser
  * add more highlight and snippets tests
Merge pull request #90 from mulesoft/bugs/not-all-valid-HTTP-methods-are-supported

Add full support of methods defined in RFC2616 and RFC5789 as per RAML spec