Get the nouns right.
Update authentication checks for new API responses.

Pushover needs better documentation for their responses.
Merge develop into master.
Update history.
Merge branch 'master' into develop

* master:
  Update history.
  Update authentication checks for new API responses.
  Get the nouns right.
Update Pushover priorities, add `chump.LOWEST`.
Add `Application.{limit,remaining,reset}` to track message allotment.

See: https://pushover.net/api#limits
Fix title and message length validation.