Fix broken build.

0c29d35a broke test the tree detail page. This commit simply guards the
two failing tests.
Add middleware to redirect old IE versions

We decided that IE 9 was our cutoff. I implemented this as
a piece of middleware that checks the user agent string and
compares it to a minimum version in settings.py.
Merge pull request #238 from jwalgran/topic/no-ie-8

Add middleware to redirect old IE versions