Clean up rubocop offenses

[simmerz]

This PR cleans up various rubocop offenses

I've also regenerated the .rubocop-todo.yml so it's up to date and doesn't contain things that have been fixed by cleaning up code elsewhere.

[simmerz]

@lcreid I've done a load of work refactoring here and am now left with 2 files that I think should be in test/ - bootstrap_deferred_builder_test.rb and bootstrap_error_rendering_test.rb

Is there any reason those are in the root of the project?

[lcreid]

Ouch! Those were test files that I was using locally at some point. I obviously should have moved them out of the tree completely, because somewhere along the line I committed them by accident. Sorry. Feel free to remove them. Or let me deal with it later.

[simmerz]

Ah ok. I did wonder seeing as I couldn't see how they could possibly pass! I'll remove them in a bit and then we're done with the to-do file.

[simmerz]

@lcreid all done

[lcreid]

Awesome work! This code is so much easier to read. It's a pleasure to read it now. I especially like what you've done for check boxes and radio buttons. That was hard code to figure out.

The only changes I think we need to do are the ones around what we declare to be HTML safe. You'll see the detailed comments below. If making the changes I asked for breaks a test case, then we need to discuss. As always, please push back if you think I'm asking for the wrong thing, or if I'm missing something.

[simmerz]

@lcreid Updates pushed. Thanks for the review!

[lcreid]

Once again, a big thanks for all the work you've done on this gem!