* Proofread and adjusted the introduction and homepage tours.
* Updated @Community links to link to the send new message page.
* The introduction tour will now always run before any specified tour (if it hasn't happened yet) and then after it finishes run the specified tour too.
* Clicking the Exit button now doesn't incorrectly mark a tour as completed.
* The default "Continue" button now says "Finish" on the final step of the tour.
* Moved the completion status from
TOURS.md to the issue tracker.
* Added a Mozilla Addons badge to the Readme.
