$CLOJURE was passed to java -classpath, which
caused the $CLASSPATH ENV var to be ingored.
This is needed for the clojure-contrib formula,
and for using third-party classes, which is kind
of useful..
brewkit.rb changes ENV destructively, so lets not do that everytime a formula
is required. Now it's possible for other tools to require a formula
description without worrying about side-effects.
Merged the clj_repl and clj commands into one clj command, which either
invokes the REPL, or runs a script (similar to how the python command works).
Moved the script to DATA, instead of inline
