-h flag throws error

[ethanagb]

prints usage lines, but then gives following traceback:

Traceback (most recent call last):
  File "../v1/generate_chrdist.py", line 58, in <module>
    GenerateChrDist(sys.argv[1:])
  File "../v1/generate_chrdist.py", line 20, in GenerateChrDist
    with open(infileName,'r') as infile:
IOError: [Errno 2] No such file or directory: ''

Seems to be still looking for -i file, but shouldn't be

[ethanagb]

Added sys.exit(2), fixed arg parsing