Flatten config variables in yml files

[maureendugan]

Flattening the variables in the yml files constitutes a breaking change. But I wanted to ask - should the variables stored in themes/*/settings.yml be moved to config/secrets.yml?

See the previous discussions for pull request #274 and the original issue #158

[reidab]

The stuff in themes/*/settings.yml should be specific to the theme itself. We'd originally thought that this would include things like the site name and the timezone, but I think most of these make more sense moving into the deployment-specific config directory.

The only thing I think it makes sense to leave in the theme settings file is the precompile_assets key. This value shouldn't need to be customized outside of version control, so it will be save to use the existing SettingsReader class to parse it.

[maureendugan]

In line with the discussion of turning Calagator into an engine... Let's merge the current PR and the next steps will be to:

1. Add figaro to call secrets and settings from ENV variables instead of settings_reader.rb and secrets_reader.rb
2. Create an initializer in the 'config' directory of the enclosing app (i.e. "some-calagator.org").

[botandrose]

👍 I'd like to see this merged so we can replace the secrets system with Figaro in the engine.

[reidab]

@botandrose do you think we should work on merging this now and rebase the engine work on top of it, or work on merging the engine work and then rethink settings in that context?

[botandrose]

@reidab I just spoke to Maureen, and I'm leaning towards merging the engine work first, and then she and I can revisit this afterwards.

[maureendugan]

Rebased these changes.

[botandrose]

👍

[coveralls]

Coverage remained the same at 100.0% when pulling 67a748d on moedu23:flatten_config_variables into 7a25f19 on calagator:master.