Resolve review comments
Merge pull request #257 from apiaryio/pksunkara/mson

Implemented MSON section parsers
Started on AttributesParser
Finished Attributes parser
Implemented attributes in Payload section
Implemented attributes in Action section
Implemented attributes in Resource section
Finished DataStructures Parser
Fix a bug when type sections present in named types
First pass WIP
Finished first pass named types table gathering
Transfer the AST changes to attributes branch
Minor review fixes