Version bump of spark-ec2 scripts

This will allow us to change things in spark-ec2 related to the 1.0 release.

Author: Patrick Wendell <pwendell@gmail.com>

Closes apache#809 from pwendell/spark-ec2 and squashes the following commits:

59117fb [Patrick Wendell] Version bump of spark-ec2 scripts

ec2/spark_ec2.py

@@ -443,7 +443,7 @@ def setup_cluster(conn, master_nodes, slave_nodes, opts, deploy_ssh_key):
 
   # NOTE: We should clone the repository before running deploy_files to
   # prevent ec2-variables.sh from being overwritten
-  ssh(master, opts, "rm -rf spark-ec2 && git clone https://github.com/mesos/spark-ec2.git -b v2")
+  ssh(master, opts, "rm -rf spark-ec2 && git clone https://github.com/mesos/spark-ec2.git -b v3")
 
   print "Deploying files to master..."
   deploy_files(conn, "deploy.generic", opts, master_nodes, slave_nodes, modules)