Chicken faster completions

This is a partial fix for #100 (closed)

Basically, the cause of the problems was too much regex. Sadly, the entirety of the issue cannot be undone due to the use of regex within the apropos egg. There remains some possibility of minor gains in the chicken geiser implementation, but nothing within two order of magnitude of the apropos slow down.

However, as a result of the changes in this PR I witnessed geiser-autdoc and geiser-completions drop from 1.3 seconds to 0.25 seconds, in the nightmare environment. Thanks to the addition of memoization, subsequent calls with the same parameters take 0.001 seconds. Memoization is cleared whenever requests are processed that may change the environment.