Add ultratrace2 entrypoint

[calebho]

Add and entrypoint console script to setup.py. Once installed, the user can invoke the program as follows:

(ultratrace) ➜  ultratrace git:(entrypoint) ultratrace2 -h
usage: ultratrace2 [-h] [--no-audio] [--no-dicom] [--no-textgrid]
                   [--no-spectrogram] [--no-video] [--theme THEME]
                   [--max-undo-memory MAX_UNDO_MEMORY]
                   path

positional arguments:
  path                  path (unique to a participant) where subdirectories
                        contain raw data

optional arguments:
  -h, --help            show this help message and exit
  --no-audio            don't try to load the audio widget
  --no-dicom            don't try to load the dicom widget
  --no-textgrid         don't try to load the textgrid widget
  --no-spectrogram      don't try to load the spectrogram widget
  --no-video            don't try to load the video widget
  --theme THEME         TtkTheme to use for application
  --max-undo-memory MAX_UNDO_MEMORY
                        number of operations to remember in the UndoManager
(ultratrace) ➜  ultratrace git:(entrypoint)

[calebho]

Closes #102