format templates to follow Drupal practices

[markconroy]

Closes #122

[andybroomfield]

This is really good, thanks @markconroy.
If we can get the tests passing again, I think it is just changing the class of several elements it looks for when checking if the banner is present and the hide button, then this should be good to merge.

[markconroy]

@andybroomfield I've changed one test where I could see the class needed to change, but tests seem to be still breaking. Could you fix that by any chance?

[andybroomfield]

Sometimes we have to re-run the tests if the tests have been changed, maybe something to do with paratest? @stephen-cox

[markconroy]

Looks like it passed.

@andybroomfield if you're okay with this now can I leave it to you to merge this for the release?

If anyone is using localgov_theme, they will need to update their CSS classes - I think the only one might be changing localgov_alert_banner to localgov-alert-banner.

Thanks a lot. I'm really happy with how this module has turned out. Great work.