Update EC2.md
Update EC2.md

Change from 
spark.executor.extraClassPath
/root/ml-matrix/target/scala-2.10/mlmatrix-assembly-0.1.jar:/root/ephemeral-hdfs/conf

to
  
spark.executor.extraClassPath
/root/ml-matrix/target/scala-2.10/mlmatrix-assembly-0.1.1.jar:/root/ephemeral-hdfs/conf
amplab/ml-matrix