C-c C-e should use the region when active.
Catch jedi.NotFoundError when using jedi's get_usages.

Jedi throws that error if it can't find a symbol at point, which
is fine and should just return "no matches".
Jedi debug info: If we have none, say so.

Used to be we just didn't emit anything, which was confusing.
Make elpy-test-runner a safe local variable.
Django test runner: Pass --noinput argument.
rope/get_definition: Catch BadIdentifierError.

Fixes #245.