Added t2 instance types

New t2 instance types require HVM amis, bailout assumption of pvm
causes failures when using t2 instance types.

Author: Basit Mustafa <basitmustafa@computes-things-for-basit.local>

Closes #1446 from 24601/master and squashes the following commits:

01fe128 [Basit Mustafa] Makin' it pretty
392a95e [Basit Mustafa] Added t2 instance types

Conflicts:

	ec2/spark_ec2.py