Allow local executables execution

Using [HomeBrew](https://github.com/Homebrew/homebrew) and brewed ruby installation, the `pod` executable resides in _/usr/local/bin/pod_ instead of _/usr/bin/pod_.
I tried appending _/usr/local/bin_ into the environment *PATH* (CCPShellHandler.m), but it seems like NSTask's _launchPath_ only accept absolute paths.