Add Sass and Specljx

Related to: https://github.com/plexus/chestnut/issues/25
This is not ready to merge, and should probably be split into 2 independent PRs.

This PR integrates Sass in a comparable way to Less.  However, the sassc API changed with 3.0.2 and lein-sassc is broken (my fork https://github.com/aew/lein-sassc is not pushed to clojars, nor have my changes been merged into the canonical).  More conditionals.

This PR also integrates speclj / specljs but does not give additional test framework options.  Even more conditionals.  Credit: http://fixitwithcode.com/posts/clojurescript-hit-the-ground-running

That said, the sass autocompilation works for me, as does autotest for clj and cljs, so I'm opening this PR to get some feedback.