Fix for ensure_bash_profile (#8)

Made it a little bit smarter about creating the dot file, first checking for
bash's in the correct order, then .zshenv.  It then looks for .profile and will
create one as a last resort if it can't find even that to update.
Merge pull request #22 from ninjabong/fix_ensure_bash_profile

Fix for ensure_bash_profile (Fixes #8)