Add spec for rendering views with partials

* Add partials fixture
Add Hyperloop::View::Scope
Add Hyperloop::View::Scope#render for partials

* Require the current request to be passed to Hyperloop::View#render
* Add mock_app and mock_request to spec helpers
Get Scope#render working just in spec
Add View::Registry
Move view lookup logic from app to Registry
Fix typo in registry spec
Add nonroot view to partials fixture
Split up registry store into templates + partials
Make find_template_view not return partials

* Add View#partial?
* Strip leading underscore in View#name
Don't let Registry return layout as a view
Use File.dirname instead of split in Registry init
Add docs for Registry#find_template_view
Add Registry#find_partial_view
Tweak docs for Registry#find_template_view
Get render working for views containing partials

* Make View and Scope know about the current view registry
* Add mock_view_registry spec helper
* Don't accept leading slashes in View::Registry#find_partial_view
Add view spec for rendering partials

* Don't load layout data for partials in View.new
* Handle nonexistent nodes in text_in spec helper
Add spec for Scope#render
Fuck you old PHP habits
Remove Bundler-generated comment from root module