Fix boolean coersion in unary not operator
Merge pull request #750 from xzyfer/fix/if-not

Fix boolean coersion in if not operations
Fix missing header for MinGW
Merge pull request #751 from mgreter/test/fix-mingw

Fix missing header for MinGW
Add some files to cache for AppVeyor

MinGW download failed from time to time!
Merge pull request #753 from mgreter/test/appveyor

Add some files to cache for AppVeyor
Fix reported file path to actual loaded file-name
Implement @debug statement analog to @warn statement
Improves @warn and @debug message to match ruby sass

Moved static get_cwd function to Sass::File namespace
Merge pull request #755 from mgreter/feature/debug-statement

Implement @debug statement