EMR: Add cluster state filters shortcut --active, --terminated and --failed in list-clusters command.
EMR: Removed Version from Applications schema.
EMR: Added default configuration for create-cluster. Fixed create-cluster.rst format. Added shortcut options --instance-type and --instance-count to --instance-groups.
EMR: Add MasterPublicDnsName in describe-cluster output.

EMR: Refactor sshutils.
EMR create-cluster: Change --visible-to-all users to be true by default.
Squashed commit of the following:

commit a86a63b311362daebf8f32affa6cbeb863860a6e
Author: Craig Foster <foscraig@amazon.com>
Date:   Tue Aug 5 14:59:01 2014 -0700

    Add helptext description, which says leaving instance-count creates one node cluster; sanitizing add-tags example

commit b004facd86051d7cfba43338a9b9543c8822834a
Author: Craig Foster <foscraig@amazon.com>
Date:   Tue Aug 5 13:56:34 2014 -0700

    Edit/change example text for create-cluster and add-tags
EMR: Removed Version from step schema.
Further cleanup of help text.
Merge branch 'emr' of ssh://git.amazon.com:2222/pkg/AWSCLIDev into emr
Merge branch 'emr' into release-1.4.0
Move emr out of preview.
Fixed a couple unit tests.
Bumping version to 1.4.0
Merge branch 'release-1.4.0' into develop

* release-1.4.0:
  Bumping version to 1.4.0
  Fixed a couple unit tests.
  Move emr out of preview.
  Further cleanup of help text.
  EMR: Removed Version from step schema.
  Squashed commit of the following:
  EMR create-cluster: Change --visible-to-all users to be true by default.
  EMR: Add MasterPublicDnsName in describe-cluster output.
  EMR: Added default configuration for create-cluster. Fixed create-cluster.rst format. Added shortcut options --instance-type and --instance-count to --instance-groups.
  EMR: Removed Version from Applications schema.
  EMR: Add cluster state filters shortcut --active, --terminated and --failed in list-clusters command.