Prototype of workshop homepage validation.

1.  Refactored `tools/check.py` in [workshop-template](https://github.com/swcarpentry/workshop-template) to separate validation checks from command line use.
    *   See [PR 105](https://github.com/swcarpentry/workshop-template/pull/105) against workshop-template.
    *   **To do:** use Python logging instead of global `Error_Messages` variable.
2.  Copied `check.py` into `workshops`.
    *   **To do:** manage this better *without* submodules.
3.  Added view to run validation on a particular event.
4.  Allowed manual override of URL to check via query parameter `?url=https://github.com/something/something`.
5.  Created [https://github.com/swcarpentry/badly-formatted-workshop](https://github.com/swcarpentry/badly-formatted-workshop) for testing.
    *   Run test by going to [http://127.0.0.1:8000/workshops/event/2015-01-14-oxford/validate?url=https://github.com/swcarpentry/badly-formatted-workshop](http://127.0.0.1:8000/workshops/event/2015-01-14-oxford/validate?url=https://github.com/swcarpentry/badly-formatted-workshop).