Add join/leave UI on community pages; #905

This uses a hard refresh of the page to update state. Maybe we'll have a
nice framework for doing that on-page some day (Angular? #833).
Bump version to 8.1.7
Bump version to 8.1.7-dev
Remove errant whitespace; #905
Bump version to 8.1.8
Bump version to 8.1.8-dev
Include unreviewed in current_communities; #910
Allow js to read username cookie; #905

We need to allow this in order to use the username in js, which is the
point of setting that cookie.
Bump version to 8.1.9
Bump version to 8.1.9-dev
Add columns to paydays for pachinko; #896

We need to start tracking this separately. The past two weeks it's
gotten double-counted with overall volume.
Count pachinko separately; #896

This counts pachinko transfers and volume separately from normal
transfers.
Add current_tips view to complement backed_tips
Fix regression in funding goal knob; #725

The jQuery.html method returns only the HTML of the first-selected
element. With two label elements in play, we need to do things a bit
differently.
Expose UI for switching to "We are"; #502
Bump version to 8.2.0
Bump version to 8.2.0-dev
Fix labels on goal knob

They were reversed for the zero and null cases.
Use goal < 0 to mean "no tips, please"; #893

This doesn't enforce no tipping throughout the app but at least enables
turning it off in the UI.
Bump version to 8.2.1