Adds basic analytics framework (mixpanel)

- Tracking launch event, with arguments passed
Fixes travis build by installing mixpanel
Adds browser and platform info to analytics
Adds analytics note to README
Adds information about --dnt switch
Tracks url visit event
Fixes link to analytics wiki page
Fixes a minor bug with the visit event

- Analytics is no longer static.
Adds firefox module that checks urls
Fixes some indentation in chrome module
Uses firefox module in the main app.
Adds editorconfig to take care of indentation.
Adds firefox flag instructions and notes to readme
Uses constants in chrome config
Merge branch 'firefox'

Conflicts:
	hackertray/chrome.py
Merge branch 'analytics'

Conflicts:
	README.md
	hackertray/__init__.py
Bumps version to 3.0.0