EMR: Add support for --emrfs in create-cluster command.

EMR: Update AMI version used in create-cluster --emrfs example.
Merge branch 'release-1.4.3' into develop

* release-1.4.3:
  Bumping version to 1.4.3
  Updated the changelog for new features.
  EMR: Remove UnknownApplicationError
  EMR: Update modify-cluster-attributes error message.
  EMR: Update help text and examples. 1. Add helptext description, which says leaving instance-count creates one node cluster; 2. Sanitizing add-tags example 3. Edit/change example text for create-cluster and add-tags
EMR: Use region from profile for when global argument is not passed when building EMR applications
Merge branch 'emr' into release-1.4.4
Updated changelog for new feature.
Bumping version to 1.4.4
Merge branch 'release-1.4.4'

* release-1.4.4:
  Bumping version to 1.4.4
  Updated changelog for new feature.
  EMR: Use region from profile for when global argument is not passed when building EMR applications
  EMR: Add support for --emrfs in create-cluster command.