Create a default rake task that lints and runs tests
Create a default rake task that lints and runs tests

This offers a close approximation as to what runs in CI for Whitehall.
Most GOV.UK apps use the default rake task to run CI checks however
Whitehall is special in this regard, this task is added to provide a
higher degree of consistency.

These tests seem to require assets:precompile to be run before the test
suite otherwise one test fails due to [1].

[1]: https://github.com/alphagov/whitehall/commit/ec98c5045eee19e17ac1e7edb82dc86cb8eeb15c

alphagov/whitehall,alphagov/whitehall,alphagov/whitehall,alphagov/whitehall