Fixed the Jython 2.7 binary to set JYTHON_HOME correctly

JYTHON_HOME is unset by the default Jython script, due to some weird ways of resolving symlinks:

    ± jython --help
    expr: syntax error
    expr: syntax error
    /usr/local/bin/jython:  contains neither jython-dev.jar nor jython.jar.
    Try running this script from the 'bin' directory of an installed Jython or 
    setting $JYTHON_HOME.

This PR fixes that issue by using greadlink to achieve the fix.

The patch is in [this gist](https://gist.github.com/offbyone/6432986/raw/70fd9bbeee6e0108322e4711f9749fcf5d632343/jython2.7+homebrew+patch)