upgrade Aspen to 0.26.x

[chadwhitacre]

We've released a new version of Aspen:

https://github.com/gittip/aspen-python/blob/master/Changelog.md#026---released-fri-sep-27-by-pjz

This has a number of changes, the most significant of which is that we now use unicode_literals everywhere. This is more than a trivial upgrade. We've already found one regression related to unicode handling and we're likely to find more, so let's shake this out pretty well on Gittip before we land the upgrade.

Once we have this landed we can get to adding unicode_literals (etc.) here on Gittip (#158).

[chadwhitacre]

We've released an 0.26.1 version with a fix for the regression mentioned above.

[chadwhitacre]

Deployed.

[chadwhitacre]

Reopening to wait for sentry emails per @zwn in IRC.

[chadwhitacre]

Nevermind. We'll reticket. :-)