Merge branch 'release-1.5.2' into develop

* release-1.5.2:
  Bumping version to 1.5.2
  Updated Changelog with new features.
  EMR: Updated test for describe-cluster
  EMR: Fix describe-cluster
  EMR: Add validation logic in steputils and clean up create-cluster and add-steps examples.
Update get_waiter to use new interface

I've added tests for this function (was previously untested)
to ensure we don't regress on this again in the future.
Update CHANGELOG with bugfix
Call super() in ConfigureCOmmand

Fixes an issue when you try to access the arg_table property,
which was breaking our html doc builds.
Merge branch 'emr-waiter' into develop

* emr-waiter:
  Update CHANGELOG with bugfix
  Update get_waiter to use new interface
Merge branch 'configure-arg-table' into develop

* configure-arg-table:
  Call super() in ConfigureCOmmand
Add retry bugfix to the changelog
Fix wrong use of super for exact-timestamps sync
Update the change log with fix
Merge pull request #964 from kyleknap/exact-timestamps

Fix wrong use of super for exact-timestamps sync
Update changelog with latest features.
Bumping version to 1.5.3
Merge branch 'release-1.5.3'

* release-1.5.3:
  Bumping version to 1.5.3
  Update changelog with latest features.
  Update the change log with fix
  Fix wrong use of super for exact-timestamps sync
  Add retry bugfix to the changelog
  Call super() in ConfigureCOmmand
  Update CHANGELOG with bugfix
  Update get_waiter to use new interface