Add notes to the "Record an Exchange" admin

The semantics of amount and fee are ... interesting. Until that's
cleaned up properly, here is a little bit of help for those of us who
have to use this form.
Here's a failing test for #2111
Here's a fix for #2111

DRY out the BalancedThings.
Fix typo in comment
Remove vestigial default arg to __getitem__

Holdover from when it was _get.
Merge pull request #2112 from gittip/fix-bank-account-regression

Fix bank account regression
Bump version to 12.1.4
Bump version to 12.1.4-dev
Move account row to a macro

The "Connected Accounts" listing includes accounts elsewhere along with
some kludged together systems (Bitcoin, Balanced). As part of #2053 we
want to group the items under Connected Accounts, but the groups don't
fall out along the lines of the accounts elsewhere/kludge split. Moving
this bit of markup to a macro gives us the flexibility we need to knit
true and kludges accounts elsewhere into the UI we want.
Merge pull request #2121 from gittip/account-row-macro

Move account row to a macro
Group accounts elsewhere under the hood

We need to axes of grouping: whether an account can be used for signing
in or not, and how to group accounts for the Connected Accounts UI. This
is a simplistic implementation of this grouping in the wireup module. It
builds on #2121, and sets us up for a next PR to implement the UI
changes to Connected Accounts (to be calved off from #2053).
Merge pull request #2122 from gittip/group-accounts

group accounts under the hood
Reorder the Connected Accounts in markup

This still isn't a user-facing change yet, but the next one should be.
This sets us up to group and restyle the Connected Accounts. Follow-on
from #2122, moves us towards #2053.
drop the website.aaaaaaand_venmo variable
Bump version to 12.1.5
Bump version to 12.1.5-dev
remove some comments of questionable usefulness
Merge pull request #2123 from gittip/reorder-accounts

reorder accounts in markup
Merge pull request #2066 from gittip/document-exchange-form

Add notes to the "Record an Exchange" admin
Merge pull request #2113 from gittip/bring-back-travis-jstest

Bring JS tests back to Travis