Moving some methods to separate extensions

[jwoertink]

Fixes #65

This breaks out the methods that require Lucky, Avram, or Authentic being required. Now you would just require the specific extension you need.

For most apps, it's an easy change:

# spec/spec_helper.cr
require "spec"
require "lucky_flow"
# Add these 3 lines
require "lucky_flow/ext/lucky"
require "lucky_flow/ext/avram"
require "lucky_flow/ext/authentic"

If you're using Lucky, but without Avram or Authentic, just add the require for lucky.

Another PR will need to go up to LuckyCLI to include these. I'll open that next.

[jwoertink]

no clue why those 2 specs cancelled... I didn't cancel them. Also looks like maybe some issues with Crystal nightly? :thinking: