Added Compass @if $legacy-support-for-ie6 and @if $legacy-support-for-ie7 to _formalize.sass

* Added compass `@if $legacy-support-for-ie6` and `@if $legacy-support-for-ie7` to `_formalize.sass` and `_formalize.scss` so you can have a hack free css file if you don't need to support these browsers. Added this to the compass_formalize repo and gem too.