Update docs/who_uses.rst

Added dbpatterns to who uses
Ignore the env3 virtualenv.
Backfilled release notes.
Added release notes for v0.9.15.
Bumped version to v0.9.15!
Started v0.9.16-dev.
Merge pull request #812 from fatiherikli/patch-1

Added dbpatterns to the Who Uses docs.
Add (failing) test for unicode support in Resource.method_check
Support unicode HTTP method names in Python 2.x (fixes toastdriven/tastypie#935)
Merge pull request #936 from kennknowles/unicode-upper

Support unicode HTTP method names in Python 2.x