Avoid clash of edit alias with TextWrangler.app edit command

**Problem**

The OS X editor [TextWrangler](http://www.barebones.com/products/textwrangler/) allows to install a command line tool (/usr/local/bin/edit) which allows to open files in TextWrangler from the command line. Unfortunately, the 'edit' alias' of bash-it defined in aliases/available/general.aliases.bash clashes with TextWranglers edit command. 

**Solution**

The fix in the pull request just unaliases 'edit' if an edit command of TextWrangler is encountered in the before-mentioned path. I fixed the problem in a similar fashion to the firefox unaliasing in osx.aliases.bash.