Added support for reduced page sizes in DDB.

This allows for faster responses & from a large scan/query drowning out other requests.
Fixed an inheritance bug in mturk.
Bumped to 2.21.2!
Merge branch 'ddb-max-page-size' into develop
Fixes #1949.
Properly handle getopt long options in s3put

Fixes #1946, where `-r` was mistakenly processed as if `--region` had been
passed because of incorrectly initialized tuples.
Merge pull request #1950 from danielgtaylor/s3put-opts

Properly handle getopt long options in s3put. Fixes #1950, #1946.
Proper string parameter handling in connection.
fix typo in docstring for ssh_client.run
Merge pull request #1953 from kanzure/fix-sshclient-typo

Fix typo in docstring for SSHClient.run. Fixes #1953.
Add unit test for unicode calling format
Merge pull request #1954 from danielgtaylor/kdeldycke-string-parameter-s3

Fix unicode string parameter handling in S3Connection. Fixes #1954, #1952.
Add missing parameters to get_spot_price_history method.  Fixes #1957.
Fix string type tests.
Merge pull request #1958 from garnaat/fix-1957

Add missing parameters to get_spot_price_history method.
Merge pull request #1959 from kdeldycke/basestring-test

Fix string instance tests. Fixes #1959.
Clarifying documentation for CloudWatchConnection.list_metrics().

- Multiple values for the same dimension are not supported by the API
- Max 10 dimensions allowed
Updated Autoscaling for the latest API changes.
Release notes for 2.22.0.
Bumped to 2.22.0!
Added Autoscale Tag class to API docs