Test commit karma for Spark git.
Merge remote-tracking branch 'old/master'
Merge remote-tracking branch 'old/master'
Merge remote-tracking branch 'old/master'
Removed repetative import; fixes hidden definition compiler warning.
Fix hash bug - caused failure after 35k stages, sigh
Address review comments - rename toHash to nonNegativeHash
updated content
Adding algorithm for implicit feedback data to ALS
Construct shell commands as sequences for safety and composability
Generate new SSH key for the cluster, make "--identity-file" optional
Work in progress:

- Add job scheduling docs
- Rename some fair scheduler properties
- Organize intro page better
- Link to Apache wiki for "contributing to Spark"
More fair scheduler docs and property names.

Also changed uses of "job" terminology to "application" when they
referred to an entire Spark program, to avoid confusion.
Added cluster overview doc, made logo higher-resolution, and added more
details on monitoring
Some tweaks to CDH/HDP doc
Ganglia sink
Review comments
Add better docs for coalesce.

Include the useful tip that if shuffle=true, coalesce can actually
increase the number of partitions.

This makes coalesce more like a generic `RDD.repartition` operation.

(Ideally this `RDD.repartition` could automatically choose either a coalesce or
a shuffle if numPartitions was either less than or greater than, respectively,
the current number of partitions.)
Adding more docs and some code cleanup
Updated cluster diagram to show caches