Tiny refactor and method extraction

Extracts the similar behavior from #instance_methods_from_modules
and #class_methods_from_modules into #methods_from_modules.

Uses compact syntax for iterating with #map.

And... <3 it.  I'll use this every so often!
I tested it & it works as expected. What it really becomes is `map(&:instance_methods)` b/c the var is just a symbol :smile: .