Firefly-client

Release Notes:
- Updates in documentation
- Update imports in demo notebooks to cleanup python 2 compatabilty code, and updated initialization to `FireflyClient.make_client()`
- Fixed errors in `show_xyplot`, `show_histogram`, `set_pan`, `set_stretch_hprgb` methods
- Added `set_color` and `set_rgb_colors` methods for changing image color attributes

Release Notes:
- `Plot.py` no longer attempts to guess or create a current `FireflyClient` instance
- You must use `useClient()` in `Plot.py` to set a `FireflyClient` instance for the other functions
- small amount of clean up

Release Notes:
- fix bug: crashed when generating a new channel ([PR](https://github.com/Caltech-IPAC/firefly_client/pull/48))

Release Notes:
- fix bug in `show_chart()` causing a stack trace

Release Notes:
- Add support for shortcut keys in `add_extension()`
- Fixed bug with "launch external tab" from lab
- DM-29655: fixed but with giving wrong url `display_url()`
- method to reopen a close lab tab `show_lab_tab()`
- Improved JSON error handling
- Improved debug support, set debug mode with `FireflyClient._debug = True`

Internal improvements:
- More testing code
- Massive clean up of constructor and factory methods
- Broke up firefly_client into 4 files
- main code, api unchanged
- `env.py` - all evironmental access in one place
- `fc_utils.py` - simple utils used thoughout code
- `fcws.py` - handles web socket callbacks
- `range_values.py` - handle range values serilaization and deserilaization

Release Notes:
- Pass the authentication token (if available) when creating a web socket
- Replace `ws4py` with `websocket-client`
- Add better exception handling around json parsing
- Add debugging option for better feedback
- Remove dependency on 'future'
- Update testing code