Bugfix: Don't warn about a failure if one didn't happen.
Merge pull request #120 from Nextdoor/fix_warning_when_actor_didnt_fail

Bugfix: Don't warn about a failure if one didn't happen.
Add warn_on_failure docs to the development doc.
Clean up logging/variable names in BaseActor
Don't raise HTTPError exceptions in the HipChat actor.

Instead, catch them properly and return False. This allows
`warn_on_failure` to work properly.
Completely R&R the Actor Return-vs-Raise Exception model.

This commit completely replaces all of our actors `raise
gen.Return(<bool>)` code with a cleaner exception raising system.
Add a HelloWorld example to the Development Docs
Add a HelloWorld example to the Development Docs
Tidy up exceptions
Add unit test for actual asynchronosity
Fixes per @siminm comments.
Raise either Recoverable or Unrecoverable exceptions in group.Async.

Based on the exceptions raised by the failed actors, we dynamically
raise either a Recoverable or Unrecoverable actor failure exception.
This allows the warn_on_failure logic to work properly, and reduces the
amount of duplicate logging we were seeing when exceptions were raised.

Additionally, quiet down duplicate logging in the
`aws.elb.WaitUntilHealthy` actor.
merge in kill_the_bools changes
Merge pull request #127 from Nextdoor/nested_exceptions

Nested exceptions
Bump version to v0.1.2
Merge branch 'master' of github.com:Nextdoor/kingpin into kill_the_bools
Bump version to 0.2.0a1
Improve group actor tests.
Oops, forgot the 0.1.2 changelog.
Merge pull request #128 from Nextdoor/improve_tests

Improve group actor tests.