[Fixes #3604] Fix nested views

[sgress454]

Now that req.view determines what to render based on what's in req.options, I don't see the utility of having a middleware function bound for each individual view, hence the removal of most of the code in lib/hooks/views/action.js. If I'm missing something, lemme know. Tests all pass without it though.

Also added new tests for using the view target syntax (e.g. '/foo': {view: 'foo/bar/baz'}) and a test for the ability to do '/foo': {view: 'foo'} and have it render views/foo/index.js if it exists--not sure if that was ever documented, but the code was is in there so I made sure it still works.

[mikermcneil]

@sgress454 looks great 🎆

Re index.ejs routing: glad to have it tested. Probably makes sense to make a note in the relevant route target documentation about this behavior as well- I'll dig that up real quick

[mikermcneil]

@sgress454 here's the change to sails-docs.

[sgress454]

🥚zellent