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 Manen dependency
Reword 'evenly distributed' to 'distributed with a hash partitioner.
Use a set since shuffle could change order.
Merge pull request #911 from pwendell/ganglia-sink

Adding Manen dependency for Ganglia
Add metrics-ganglia to core pom file
Merge pull request #912 from tgravescs/ganglia-pom

Add metrics-ganglia to core pom file
Print out more friendly error if listFiles() fails

listFiles() could return null if the I/O fails, and this currently results in an ugly NPE which is hard to diagnose.
Merge pull request #907 from stephenh/document_coalesce_shuffle

Add better docs for coalesce.
Fix copy issue in https://github.com/mesos/spark/pull/899
Style fix: put body of if within curly braces
Merge pull request #916 from mateiz/mkdist-fix

Fix copy issue in https://github.com/mesos/spark/pull/899
Merge pull request #915 from ooyala/master

Get rid of / improve ugly NPE when Utils.deleteRecursively() fails
Document fortran dependency for MLBase
Merge pull request #917 from pwendell/master

Document libgfortran dependency for MLBase
Add explicit jets3t dependency, which is excluded in hadoop-client
Update Python API features
Fix HDFS access bug with assembly build.

Due to this change in HDFS:
https://issues.apache.org/jira/browse/HADOOP-7549

there is a bug when using the new assembly builds. The symptom is that any HDFS access
results in an exception saying "No filesystem for scheme 'hdfs'". This adds a merge
strategy in the assembly build which fixes the problem.
fix run-example script
Merge pull request #921 from pwendell/master

Fix HDFS access bug with assembly build.