Bumping version to 0.10.0

This bump includes https://github.com/alphagov/govuk_template/compare/v0.9.1...c1d8d483c12bb3498ace9a020d5fbacf0f47ef55
Can this be slightly more descriptive. Something like: 'Add `display: block` to HTML5 `<main>` tags'. Then you won't need to actually look at the code to see what it means.