Revert "Require Java 7"

This reverts commit 90a1e7530e4942bdfb8b0dade5c4e76a65ccd459.
Stick to the older CLJS and 1.5.1 for the moment.

Revert "Revert "Revert "Update to Clojure 1.6.0 (now the minimum version) and CLJS 0.0-2261"""

This reverts commit ba678684026558c06c9b59f3e7a4b0fb3dc58383.
Add back Not