Require long-form partial rendering

[joeldrapper]

Closes #137

In order to render a partial, you must pass it as the partial: keyword argument.

[willcosgrove]

Should this move down to the when nil clause?

[joeldrapper]

I just caught that myself. Pushed up a change.

[bradgessler]

Yay! This cleans up a bunch of weird things I had to do in Rails to have Phlex render a string value.

[julianrubisch]

I'm late to the party here, but I just noticed that it's needed to be called like this:

render(partial: "form", post: @post)

which, AFAIK, wouldn't work in ActionView, it would require the locals keyword:

render(partial: "form", locals: { post: @post })

is it worth noting this inconsistency somewhere?

[joeldrapper]

Agh, that's annoying. I wonder if it would be better for us to support this instead

render partial("foo"), ...

[julianrubisch]

That would be more consistent, but I think it just boils down to adding it to the docs

[joeldrapper]

Thanks for catching this. We should get it right before the 2.0 release.