Thank you page templates

* Removes distinct thank you/failure pages for different fund types; all run through a single url/template now
* Enforce trailing slash; other pages will be automatically redirected
* Passes along the donor's first name with the url. This will be checked when rendering the success page
* Add the request to the context middleware -- making the above possible
* Simple templates for the projects and fund thank you pages
* Links to facebook/twitter, sharing the project/fund's "detail" view
* Setting to edit the twitter share text