Replace simplegeneric with singledispatch (PEP 443).

Closes-Bug: #1226813
Change-Id: I1ba149ac00353460065d4cddbe3ccd8782aaa611
Squeeze some more performance out of the WSGI __call__ and dispatch algorithm.

Change-Id: I3e25381d526866d6feae05f0dcbdca5707f86df7
Update README.rst with bug/issue tracker information.

Change-Id: Ic2b3445aae4009fdf44484d52dd0b31f04ed4faa
Merge "Update README.rst with bug/issue tracker information."
Merge "Squeeze some more performance out of the WSGI __call__ and dispatch algorithm."
core: do not try to set response body to None

In the context of DELETE, it's more than likely than the response will
be empty. In such a case, setting response.body to None will fail.

Change-Id: I29fde6c448c935c40c768376a15e83337b951898
Merge "core: do not try to set response body to None"
Version increment.

Change-Id: Id6d78c43b1c4a2de75d5419c606d7af1e9c48ea1
Version increment.

Dependencies changed (we removed simplegeneric and replaced it with
singledispatch), so we should probably release a new major version.

Change-Id: Ic618d8998ec6f90806dc5fc84451f2ad616f1e66
Including a `venv` tox environment so we can release via OpenStack CI.

Change-Id: I42559526c951301a812910f4e48de8ac5221613a
Remove a routing optimization that breaks the WSME pecan plugin.

Fixes-bug: 1232199
Change-Id: Ie0f93e5b783f601fc734919db02e658222a402ba
Version increment.

Change-Id: Ieb0de1a38c5d015a8df07da9e5df7a36b6214c51
import order