Improve cljsbuild/uberjar settings

Build optimized code when creating an uberjar. Also loads react directly
from the com.facebook/react. This allowed us to clean up index.html
significantly.

The lein-cljsbuild hook is now only executed when building an
uberjar. Before it would run when starting a REPL, which means that when
starting `lein repl` and `lein figwheel` at the same time, you could get
mangled compiled clojurescript.
Update figwheel to 0.1.4-SNAPSHOT
Bump version to 0.3.0