Parse Result Release

This is a backward-incomatible release with the following changes.

Breaking

• C++ interface now returns Refract ParseResult instead of API Blueprint AST by default. You can get the previous behaviour using the NormalASTType option.
• Command line interface has changed to by default, return the whole ParseResult under both Refract and AST output types, along with source maps.

Enhancements

• Support for the nullable MSON type attribute.
  #106
• Source maps are now available when using the Refract output type with the exportSourceMap option.
  #148
• We now offer a JavaScript version of drafter using emscripten.

Bug Fixes

• Drafter should no longer raise exceptions and instead attach all errors to the parse result.
• Various bugs while rendering JSON from MSON have been resolved.
  #117
  #136
  #137
  #141
• Meta classes from an asset element are now an array as per the Refract specification instead of using the class key.
  #179