fix(channel): Make sure the web channel invokes the 'done' callback in Channel.send if it's given one
fix(constants): Added a constant for the Fx Desktop context
feat(session): Make the Session aware of the 'context'
feat(client): Don't show 'settings' when context=desktop and user is verified
fix(channel): call 'done' callback in Session.send if given
Merge pull request #699 from mozilla/issue-697

Issue 697: Don't show 'settings' landing page after a verified user logs in with context=desktop.