Correct loading of Git completions

I pretty much referred to the following to get this fixed:

  https://github.com/mxcl/homebrew/issues/16992#issuecomment-14328202

Modified it slightly so that it used `brew --prefix` instead of
hardcoding the Homebrew installation directory.

Signed-off-by: Ealden Esto E. Escanan <ealden@gmail.com>
JAVA_OPTS for memory-hungry Java apps

Signed-off-by: Ealden Esto E. Escanan <ealden@gmail.com>
Replaced ZSH prompt with the one from oh-my-zsh's simple them

I like it better than what we have here.

Signed-off-by: Ealden Esto E. Escanan <ealden@gmail.com>