Change spark-version from 1.1.0 to 1.2.0 in the example for spark-ec2/Launch Cluster.

Author: Miguel Peralvo <miguel.peralvo@gmail.com>

Closes #4300 from MiguelPeralvo/patch-1 and squashes the following commits:

38adf0b [Miguel Peralvo] Update ec2-scripts.md
1850869 [Miguel Peralvo] Update ec2-scripts.md