Added Sass converted files
Rename using leading underscores
Fixed opacity() mixin 'Invalid CSS' error (used opacity() from twitter bootstrap)
Fixed gradient() mixin by combining with twitter bootstrap (sass) solution
Tidied indenting/formatting in _mixins.scss
Commented out retina-image() mixin due to compile error in compass
Fixed striped() mixin ';' instead of ',' in variable declaration
Fixed 'Incompatible units: '' and em.' error caused by maths in _variables.scss
Fixed unconverted @include in _grid.scss
Corrected $ to @ in _progress.scss caused by earlier find/replace