Add lens dependency
Add TH for lenses
Add monoid instance for Fass.Selector
Remove SASS name prefixes
Fix SASS name prefixes
Cleanup specs for parser
Fix evaluator to remove empty rulesets

For example when unwrapping the following example

    p {
      span { color: red; }
    }

The result should be just

    p span { color: red; }

instead of

   p { }
   p span { color: red; }
Add prisms for Fass.Types.Selector
Fix printing of Selector to only include the content
Change unwrap to [Entity] -> [Ruleset]
Add specs for Compiler
Change Printer to only work with Entities
Fix compiler to work with simple SCSS

This is the first commit where all tests actually pass and sample SCSS
gets compiled into CSS :)
Fix executable main
Export Fass.Compiler from the library module
Safeguard against dashes in filenames when cleaning build
Add -Wall to .cabal builds
Cross over simple SCSS to CSS compilation