Clean up filenames for actions

I dislike having each file in ./actions ending in _action.rb. Using
namespaces is actually probably what I'll end up doing shortly.
Rename SafeAction to BaseAction
Moved helpful descriptions into actions

Considering writing a DSL for these where you do something like

class MyCustomAction < BaseAction
  on(:message, /!somethingCool/) do |m|
    m.user.reply "woah! I know kung fu"
  end

  help_should_be '!somethingCool : does something AWESOME'
end

But this puts the help messages alongside the actions, which was
roughly what I wanted to do in the first place.