Have git ignore files created by tests

When the tests are run, some packages are installed or created in the
current directory. They should never be checked in, so add them to
.gitignore.

Change-Id: Ic7790ec85c9e2f0fc4bd06b492f75ea6c17ecda4

--HG--
extra : rebase_source : 7ad1502fd5d09d38f521a391e22af46cfce6ea4f

.gitignore

+.tox
+py-*.egg
+pytest-*.egg