Added coinbase payout script
Update print statements to use print()
Use instant_buy

We don't keep any escrow in Coinbase, so we always need to buy BTC first
before we can send it along to users as a payout. We do have instant_buy
enabled. Our instant buy limit is $1,000 per week.
Coinbase script now fetches amount and fee from response
Added a note to bitcoin exchanges, and added int/string conversion for fees
Print JSON result if coinbase doesn't give a 200
deduct amount + fee from balance
added recently cancelled tips
Tests for giving page
Fix errors, check for negative balance
Switch to new OSM OAuth app for dev

The old one was called gittip-test. I can't find where it is! It's not
under the vendors@gratipay.com account, nor my personal account. O.O
Merge pull request #2820 from gratipay/osm-app

Switch to new OSM OAuth app for dev
Added i18n pluralization
Improve my-tip ui
Removed unnecessary opacity rules
Adds FAQ about why payments can decrease

This plainly establishes the mechanisms by which donations can decrease.

The aim is to eliminate accusations that anyone involved in the Gratipay
machine can wantonly interfere with someone else's donations unchecked
without prior notice, where unprohibited by law.
Merge pull request #2823 from colindean/faq-payment-failure

Adds FAQ about why payments can decrease
Reorder faq to even up the columns
Match title with anchor
Merge pull request #2828 from gratipay/reorder-faq

reorder FAQ