Changes 3.4.4:
Features
* Update Visual Studio build facade
* Update read me
* Performance improvements for @extend
* Performance improvements

Fixes
Disable FMA3 when compiling with Visual Studio 2013
Fix for loop variable to be referenced
Fix number compare issues when used as map keys with old gcc
Fix results of map-get not being evaluated
Fix null pointer access
Fix bug with media queries and @extend

Misc
Cleanup initial shared ptr interface
Refactor selector list and schema handling
Cleanup context usage and extend code
Cleanup misc
Cleanup issues detected by clangs static analyser
Remove Textual intermediate AST node
Add libsass-python to README

(adam)