Copy the _compiler.c file to the package
Merge pull request #14 from astrofrog/fix-compile-c

Copy the _compiler.c file to the package
Changes to setup_helpers.py from astropy/astropy#2223
Changes to test_helpers.py from astropy/astropy#2353, astropy/astropy#2214, and astropy/astropy#2094
Changes to test_helpers.py from astropy/astropy#2198