I needed to run some d2 instances, so I updated the spark_ec2.py accordingly

Author: Brendan Collins <bcollins@blueraster.com>

Closes #6014 from brendancol/ec2-instance-types-update and squashes the following commits:

d7b4191 [Brendan Collins] Merge branch 'ec2-instance-types-update' of github.com:brendancol/spark into ec2-instance-types-update
6366c45 [Brendan Collins] added back cc1.4xlarge
fc2931f [Brendan Collins] updated ec2 instance types
80c2aa6 [Brendan Collins] vertically aligned whitespace
85c6236 [Brendan Collins] vertically aligned whitespace
1657c26 [Brendan Collins] updated ec2 instance types