Fix invitation typo in readme
Merge pull request #715 from oMartell/master

Fix invitation typo in readme
Bump version to 3.1.0.pre to prevent confusion with master being 3.0.0 but 3.0.x releases are out.
Remove extra `once`.
Fix typo.

[ci skip]
Merge pull request #716 from rspec/remove-excess-once

Remove extra `once`.
Verifying doubles should expire just like normal doubles.
Merge pull request #718 from rspec/fix-verified-double-expiration

Verifying doubles should expire just like normal doubles.
Sketch implementation of ordered with counts
Implementation and spec cleanup for #713
Add specs for ordering with at_least and at_most
Remove unnecessary unless
Add a changelog entry for #713