Add Right To Know stats

[auxesis]

Looks like this:

This effectively deprecates the need for openaustralia/jacaranda-righttoknow.

Also:

• Split the scraper out into several smaller files, to reduce cognitive overhead for maintainers.
• Make it easy to add new runners to post stats for different applications.
• Improve the test suite coverage by testing behaviour after we time travel.

Caveats:

• This PR changes the primary key from date_posted to a composite primary key of date_posted and runner.
• I need to do further testing to see how the scraper handles this when run on Morph (the testing behaviour locally was not great).

TODO:

• [x] Update documentation to remove references to MORPH_GITHUB_OAUTH_ACCESS_TOKEN now it's not needed.
• [x] Update documentation to explain how to add new runners.
• [x] Refactor the tests to set up and tear down an in-memory SQLite database for every test.
• [x] Set up Travis to run the tests on this repo automatically.
• [x] Refactor rspec to use context per https://github.com/openaustralia/jacaranda/pull/4#discussion_r133113954

[equivalentideas]

@auxesis this sounds really good to me 👍

[auxesis]

@equivalentideas feeling good about where this is at.

Ready for review.

[equivalentideas]

@auxesis currently the readme talks about the information Jacaranda tells you about PlanningAlerts usage, but as we're including Right To Know data now it should talk about that too.

[auxesis]

Closing in favour of #8, which addresses all the concerns listed by @equivalentideas above.