New feature: API Rate Limiting, auto-retry

[afinkenstadt]

cf: https://developer.atlassian.com/hipchat/guide/hipchat-rest-api/api-rate-limits

implement automatic retry when API rate limited

pull request to come, unless it's already in queue

[afinkenstadt]

@tbruyelle

I plan to add another hipchat package variable which controls whether to do retries on HTTPStatusCode 429, in the same style as the AuthTest. I'll also add a place to record the latest returned headers to allow inspection by the host program using hipchat-go.

X-Ratelimit-Limit: 100
X-Ratelimit-Remaining: 69
X-Ratelimit-Reset: 1476919340

Any objection?

[tbruyelle]

Nope