Added modules that would lead to setuptools being imported to the unsafe import list in configuration file generation, since if setuptools is not installed, it is *not* downloaded automatically at runtime (and this causes issues if importing astropy for the first time and generating the configuration file).
Fixed setup_helper -> setup_helpers and version_helper -> version_helpers
Merge pull request #651 from astrofrog/config/fix-no-setuptools

setup.py build fails without setuptools installed?