Don't crash if the connection has an error
set encrypted flag to None for root device

"AWS API doesn't support any value for this flag for the root device of
a new instance"

see: boto#2587

closes gh-455
move try/except from is_up to is_ssh_up
Merge branch 'fix-conn-reset-by-peer' into develop

closes #465
remove t2 types from placement group types list
bump version to 0.95.6
Changelog: update for 0.95.6 release
Merge branch 'hotfix-0.95.6' into develop
Added ability to override spot-bid and instance-type from command line
hack to fix problem where terminate —force fails
Bug fix for exception thrown in get_impaired_nodes that occurs when there are >100 nodes.

AWS doesn’t allow for more then 100 instance ids to be specified at once.
Merge tag '0.95.6' into minor-fixes to include fix for newer versions of boto

release 0.95.6

Conflicts:
	starcluster/static.py
Merge branch 'vanilla-minor-fixes' into vanilla_improvements