Use a specific envvar instead of TESTING

We should use fine-grained environment variables instead of general ones
like "TESTING."
Merge pull request #2535 from gittip/typography-change

#2457 - Swap Helvetica Neue with Ideal Sans
Bump version to 13.2.6
Bump version to 13.2.6-dev
#2545 - don't wrap content in .you-are
Merge pull request #2546 from gittip/profile-ideal-truncate

fixes #2545
Bump version to 13.2.7
Bump version to 13.2.7-dev
upgrade Aspen to 0.32
Here's a first pass at upgrading to Aspen 0.32

I went with gunicorn for a web server, because it is much simpler to
configure than uwsgi. Note that this Makefile requires a patched version
of Honcho. I made a PR but I don't know if it will be accepted:

https://github.com/nickstenning/honcho/pull/71
I'm adding a file!
remove our temporary copy of to_rfc822()
Use new json_dump renderer in error.spt
Reformat JSON simplates

With this newer version of Aspen we no longer have special-cased JSON
simplates. Instead they are now regular rendered/negotiated simplates
that utilize a json_dump renderer.
Test and upgrade api-key.json
Test and upgrade the members/index.json endpoint
Test and upgrade about/paydays.json endpoint
Test and upgrade tip-distribution.json endpoint
Upgrade to our forked version of Honcho

See https://github.com/nickstenning/honcho/pull/71.
check Heroku environment before deploying