Handling cases where herd.py is symlinked to another location

When making this a python package, it was trying to reference the symlinked location instead of the actual location of herd.py.

For example, if we put /usr/bin/herd as a symlink to /usr/lib/python<version>/site-packages/herd/herd.py, we want to reference the true location instead of the symlinked location.