Rough in UI for account cancelation; #54

Now that the three scripts involved in account cancelation have been
moved to (tested) methods on Participant, we're ready to wire up the UI.
This commit rebases the original work we did on the UI on top of the
separate line of development we ended up pursuing for the Participant
methods.
Rough in UI for case where there is no balance
Fill out verbiage on cancel page

Based on conversation in IRC:

https://botbot.me/freenode/gittip/2014-06-06/?msg=15781294&page=1
Note more things we need to delete during cancel
Change nomenclature from "cancel" to "close"

Decided in IRC to use this verbiage:

https://botbot.me/freenode/gittip/2014-06-06/?msg=15785179&page=3
Add border to red button to make it a button

Looked like a link before.
Drop js confirm for account close

We have a whole confirmation page, we don't need the js confirm.
Clarify wording around what's deleted on close
Here's the test fixture for cancel -> close
Prune vestigial disbursement strategy

I'm not going to implement this now.
remove vestigial file
update FAQ
show a message instead of redirecting to homepage
Tweak language on close page
Dial back language on Close to be more accurate

We're not able to deliver on strong "we delete all your info" promises
yet, because we haven't formalized a data retention policy (#397).
Tweak language on close page
Prune unused variables

These were actually using API that went away in #2352, but they're also
unused in the simplate anyway.
Merge branch 'master' into cancel-account

Conflicts:
	tests/py/test_close.py
Implement "Account closed" page as 410
Redirect to "Account closed" page after closing