Upgrade to at least Sass 3.3 in order to add in a 'mature' version of scss-lint

[Guntrisoft]

At present dough is depending on sass-rails.

The latest version of sass-rails (v4.04) depends on version ~> 3.2.2 of Sass

If we are to introduce scss-lint into the project (latest v0.30.0) then we need Sass 3.4

There is a version of scss-lint (v0.27.0) which supports Sass 3.3

The version which gets installed which supports ~> 3.2.2 sass is version 0.7.0 which is extremely old and doesn't allow a config file to determine which rules you wish to apply.

[ourmaninamsterdam]

Also, having 3.3+ would give us many more features that 3.2.2 currently lacks such as map data structures, @at root and Sass source maps.