Support for building on MS VS Express 2013
Set default to MSVC2012
Deprecate unsuppored MSVC versions
Fix compatibility with Python 3.x

In Python 3 `print` is no longer a statement
Merge pull request #178 from apiaryio/zdne/python3

Fix compatibility with Python 3.x
Merge pull request #175 from adamretter/master

Support for building on MS VS Express 2013
Remove direct Sundown dependency
Parser refactor orgin

The aim of this major refactor is to bring easy syntax extensibility
via parser modularity. See https://gist.github.com/zdne/55b7a38f52ca642e123b
the parser prototype.

This commit / refactor also introduces new redesigned Markdown parser – https://github.com/apiaryio/markdown-parser.
Reporting & section context parser data origin

Parsing foreign asset blocks.
Code block signature check origin. Additional asset tests.
Excessive indentation check origin
WIP: Header parser refactor in progress
Completed HeadersParser refactor
Finish HeadersParser refactored tests
WIP: PayloadParser refactor in progress
PayloadParser fixes done
PayloadParser tests are refactored
Add symbol reference support to PayloadParser
Started on ParameterParser
WIP: ParameterParser refactor almost done