[SPARK-2399] Add support for LZ4 compression.

[rxin]

Based on Greg Bowyer's patch from JIRA https://issues.apache.org/jira/browse/SPARK-2399

[rxin]

cc @davies

[SparkQA]

QA tests have started for PR 1416. This patch merges cleanly.
View progress: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/16666/consoleFull

[SparkQA]

QA tests have started for PR 1416. This patch merges cleanly.
View progress: https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/16667/consoleFull

[SparkQA]

QA results for PR 1416:
- This patch PASSES unit tests.
- This patch merges cleanly
- This patch adds the following public classes (experimental):
class LZ4CompressionCodec(conf: SparkConf) extends CompressionCodec {

For more information see test ouptut:
https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/16666/consoleFull

[SparkQA]

QA results for PR 1416:
- This patch FAILED unit tests.
- This patch merges cleanly
- This patch adds the following public classes (experimental):
class LZ4CompressionCodec(conf: SparkConf) extends CompressionCodec {

For more information see test ouptut:
https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/16667/consoleFull

[rxin]

Ok merging this in master.