2.1

Feature

• Add current_limit attribute to extension to
  allow clients to fetch the relevant current limit
  that was evaluated.
• Update extension constructor parameters to match
  flask config for header control
• Add on_breach callback for limit and shared_limit
  decorators to be used as hooks for when a limit is breached
• Add cost argument to limit and shared_limit to control
  how much is deducted when a hit occurs.

Chore

• Improve documentation around configuration

Deprecation

• Remove hacks for managing incorrectly ordered
  limit/route decorators