Rationalize Perseus idioms

[arctic-hen7]

Is your feature request related to a problem? Please describe.
If you take three seconds to go through the Perseus idiom of defining functions that return closures within Rcs, you'll probably stop liking it pretty quickly, because it's grotesque. Besides, we can trivially just have those closures as functions themselves that are then placed in Rcs (which is also an idiom, but only for some things...).

Describe the solution you'd like
In short, these idioms need to start making sense! A lot of them are left over from the old architecture of v0.1.0 and even before that, and they should be updated in the documentation and examples to reflect better practice (which is more concise and logical).

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
This is primarily a documentation change, but it's a very big one, and it'll be released in v0.3.0.

[arctic-hen7]

I'll work on this with the changes in #31.