Fix namespace Sass module due to conflict with bootstra-sass-rails

No one should really use the two together, but in case they do, or in case any other library defines a Bootstrap::Sass module, we should be clear that we mean the global core Sass module here. Fixes thomas-mcdonald/bootstrap-sass#293
Merge pull request #294 from trisweb/trisweb_fix_sass_load_path

Fix namespace Sass module due to conflict with bootstra-sass-rails