Fix cljx config

Upgrades to cljx 0.5.0, which actually supports the prep-tasks that were added
from #62. Also moves cljx config to root level of project config to make
accessible when building jar.

Creating jar from clean project left out files. It seems previous releases only
contained the right files because cljx had already ran before making jar...
Merge pull request #65 from Prismatic/fix-cljx-config

Fix cljx config