Remove Compass dep, Grunt tasks, Setup SASS_PATH.

Thanks again Sam for allowing me to contribute :heart: 

* From conversation started in issue #5. Dropped Compass. Added SASS_PATH.
* Clean root gemspec.
* Clean Minitest usage. Only a few lines of code gives us what we need. No need for tmp dirs either.
* Moved example.scss to examples dir. No need to ignore in dep files now. Does not pollute ruby Sass path in gem as it did before too.
* Changed all docs to remove compass as a dep.
* Updated all examples to use latest 0.3.2 version.
* Changed Sass dep to any 3.x version.
* No dups in Gemfile, it just uses the gemspec now.
* Etc, etc.