Improve autocomplete and add eldoc hints

[rrrnld]

Fixes an error that occured to me whenever my cursor was on an opening paren:

Company: backend company-capf error "Scan error: "Containing expression ends prematurely", 283, 283" with args (prefix)

Also adds rudimentary eldoc support for method arguments, which gets displayed as soon as you type out the method:

Crackle.ar(|)

shows chaosParam=1.5, mul=1.0, add=0.0 in the minibuffer.

[rrrnld]

Sorry for the force-pushes, I a big chunk of both files was re-formatted on save and I only noticed after opening this PR. I reverted those changes because they don't have any meaning in the context of this patch.