Adding disclaimer for shuffle file consolidation
Merge pull request #236 from pwendell/shuffle-docs

Adding disclaimer for shuffle file consolidation
Minor formatting fix in config file
Merge pull request #237 from pwendell/formatting-fix

Formatting fix

This is a single-line change. The diff appears larger here due to github being out of sync.
Correct spellling error in configuration.md
SPARK-917 Improve API links in nav bar
Merge pull request #239 from aarondav/nit

Correct spellling error in configuration.md
Merge pull request #240 from pwendell/master

SPARK-917 Improve API links in nav bar
Deduplicate Local and Cluster schedulers.

The code in LocalScheduler/LocalTaskSetManager was nearly identical
to the code in ClusterScheduler/ClusterTaskSetManager. The redundancy
made making updating the schedulers unnecessarily painful and error-
prone. This commit combines the two into a single TaskScheduler/
TaskSetManager.
Fixed most issues with unit tests
Cleaned up imports and fixed test bug
Extracted TaskScheduler interface.

Also changed the default maximum number of task failures to be
0 when running in local mode.
Fixed naming issues and added back ability to specify max task failures.
Changed local backend to use Akka actor
Fix bug where scheduler could hang after task failure.

When a task fails, we need to call reviveOffers() so that the
task can be rescheduled on a different machine. In the current code,
the state in ClusterTaskSetManager indicating which tasks are
pending may be updated after revive offers is called (there's a
race condition here), so when revive offers is called, the task set
manager does not yet realize that there are failed tasks that need
to be relaunched.
Don't retry tasks if result wasn't serializable
Fixed error message in ClusterScheduler to be consistent with the old LocalScheduler
Fixed merge