Remove dependency on 'times' library (see issue #286).

Basically, for the functionality needed, a dependency on 'times' (which
in turn depends on 'python-dateutil') seem unnecessary.
Merge pull request #287 from malthe/shed-times-dependency

Remove dependency on 'times' library (issue #286).
Ignore .envrc files.
Add wheel support to RQ.
Remove `times` dependency from requirements.txt.