updates fileutiles.walk to use glob

tested with python 2.6 and 2.7, glob appears way back in 2.3, but i don't know what version of python htools is targeting (presumably whatever robofont uses?)
Merge pull request #35 from nsfmc/globwalk

thanks. I wrote this a while ago, didn't know about glob. any contribution is welcome. if you join the mailing list, we can talk more there.