remove extra commas and add quotes around "null" key to make jshint happy
change "cut" option in Makefile to be compatible with OS X

The GNU version of "cut" allows "--bytes" or "-b", but the version in OS X
understands only "-b", so use "cut -b -6" instead of "cut --bytes=-6".
Merge pull request #88 from Survos/jshint-cleanup

remove extra commas & add quotes around "null" key to make jshint happy
Merge pull request #89 from Survos/make-osx-cut

change "cut" option in Makefile to be compatible with OS X