DataDir no default

[jwillis0720]

If you specificy a datadir and its not there, the program fails. Might I suggest making one by default like you have done for input dir and outdir and tempdir. a lot of people probably dont have the permission to modify and access root level data.

  output_dir = abstar.run_standalone(args)
  File "/dnas/apps/anaconda/lib/python2.7/site-packages/abstar-0.1.0-py2.7.egg/abstar/abstar.py", line 538, in run_standalone
    setup_logging(args)
  File "/dnas/apps/anaconda/lib/python2.7/site-packages/abstar-0.1.0-py2.7.egg/abstar/abstar.py", line 211, in setup_logging
    log.setup_logging(logfile, debug=args.debug, print_debug=print_debug)
  File "/dnas/apps/anaconda/lib/python2.7/site-packages/abtools-0.1.0-py2.7.egg/abtools/log.py", line 42, in setup_logging
    level=logging.INFO)
  File "/dnas/apps/anaconda/lib/python2.7/logging/__init__.py", line 1545, in basicConfig
    hdlr = FileHandler(filename, mode)
  File "/dnas/apps/anaconda/lib/python2.7/logging/__init__.py", line 911, in __init__
    StreamHandler.__init__(self, self._open())
  File "/dnas/apps/anaconda/lib/python2.7/logging/__init__.py", line 941, in _open
    stream = open(self.baseFilename, self.mode)
IOError: [Errno 2] No such file or directory: u'/dnas/home/jwillis/sequencing/NextSeq/joined/data/ab