Remove unnecessary '?' from req.path on POST

The if/else logic in add_auth on line 491 only handles if qs and POST.

But if you're POSTing with no query string, execution falls into the else condition on line 497 and an unnecessary '?' is added with a blank query string.

My elastictranscoder.create_job calls were failing due to the unnecessary '?' in the path. It would return:

JSONResponseError: 403 Forbidden
{u'message': u"When Content-Type:application/x-www-form-urlencoded, URL cannot include query-string parameters (after '?'): '/2012-09-25/jobs?'"}

I'm not sure why, but the bug only happens when running on Google App Engine. My local dev_appserver was able to make the create_job request just fine.
Return the StepSummaryList from this call
Dyanamo Table.scan() should accept 'attributes' argument
Updated all old-style inheritance calls.
Add unit test for STS security_token
Merge pull request #1948 from danielgtaylor/jimbrowne-sts-secure-token

Pass security token through to STS connection. Fixes #1948, #1931.
Missed two spots for use of ``super(…)``.
Merge branch 'switch-to-super' into develop
Fixes #1918, #1936 & #1937.
Add release notes script

Adds a script to find the latest release and gather all commits
from then until the latest commit, then spits out restructured
text.
Merge branch 'master' into release-2.21.1
Bumped to version 2.21.1!
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.
Merge remote-tracking branch 'upstream/develop' into consistent-identity-comparison-none

Conflicts:
	boto/manage/server.py
Proper string parameter handling in connection.
fix typo in docstring for ssh_client.run