Add Spark-yarn dependency when SHARK_YARN=true, which by default is false.
Also fix Hadoop FileSystem Sevice Meta file assembly rules.
Merge pull request #163 from AtScaleInc/master

Pull the Hadoop version from the environment.
Merge pull request #164 from colorant/yarn-assembly

add spark-yarn dependency
Fix a check in sbt/sbt (if there are multiple command line args, sbt/sbt throws an error in line 8).
Use env shortcut in build file for YARN build.
Fix hadoop conf dir path for Hadoop 2.x
Merge pull request #165 from colorant/hadoop-conf

Fix hadoop conf dir path for Hadoop 2.x