Better support for parsing complex ie function values
Merge pull request #743 from xzyfer/fix/ie-keyword-parsing-variables

Better support for parsing complex ie function values
Fix build for mingw and dll linking
Add appveyor from continuous integration on windows
Add project files for Visual Studio Community 2013

Stolen from https://github.com/darrenkopp/sassc-win
Fix build to pass tests on appveyor-ci