bugfix: support path separators in module path

As described by http://docs.ansible.com/intro_configuration.html#library the library supports multiple paths to load modules from. 

Currently `setup.py` treats something like `/usr/share/ansible:/my/custom/modules` as a single directory name and results in the installed modules not being on the module path. (instead they are in a directory named `/usr/share/ansible:/my/custom/modules`) 

This commit simply takes the first listed directory as the install directory for the core modules.
Merge branch 'patch-1' of https://github.com/eggsby/ansible into eggsby-patch-1
Tweak library installation path to default to /usr/share/ansible if specified