Remove deprecated configuration options.

Bugs closed: AURORA-333

Reviewed at https://reviews.apache.org/r/26430/
Handle resourceOffers callback asynchronsly.

Bugs closed: AURORA-848

Reviewed at https://reviews.apache.org/r/26821/
Fix redirect loop when accessing rewritten paths.

Testing Done:
./gradlew build -Pq

Also started up multiple schedulers in vagrant image and confirmed
that I'm properly redirected when accessing the non-leading scheduler.

Bugs closed: AURORA-841

Reviewed at https://reviews.apache.org/r/26790/
Draft of cron documentation