User Documentation

[jantman]

Add user documentation:

• user guide Sphinx page
  • include screenshots, with a tox env to build them (via phantomjs? chrome?)
  • include a short screencast of actually playing the game and showing the major features
• help page in app itself - start with text of features, and also point to user guide on RTD (point to the specific per-version tag)
• update features list in README
• enable RTD, get build working
• link to that page in README (prominent, near the top, as well as in the "Usage" section where there's now just a ToDo comment) and GitHub repo setting URL

[jantman]

I enabled builds on RTD, but the build is failing; need to look into this: https://readthedocs.org/projects/gw2copilot/builds/4667747/

Perhaps also look into: readthedocs/readthedocs.org#1139 (comment)

[jantman]

Add an FAQ section; first one should be missing map tiles (zoom out and back in; should be fixed with #3)

Also FAQ on caching of GW2 API calls
and on leaving it open in the background when GW2 is closed - GW2 needs to be running before you start it, but it should reconnect