Fix regression for supported timestamp formats

We now accept:

* datetime objects
* ISO8601
* epoch seconds (both as an int or a string)

anytime a timestamp type is needed.  This puts back the previous
behavior that botocore had.

To accomodate this, I've added a new date parsing utility method
in the utils module.  It accepts any of the types listed above and
returns a datetime object with tzinfo.  This makes it easy to write
protocol specific timestamp serializers as they now can assume
they'll always be working with a datetime object with time zone info.
Merge branch 'release-0.76.0' into develop

* release-0.76.0:
  Bumping version to 0.76.0
  Update service models
Merge branch 'timestamp-input' into develop

* timestamp-input:
  Fix regression for supported timestamp formats
Fix integ test failure by specifying a region
Upgrade versions of six/unittest2

Confirmed there are no issues.  Six upgrade is a backwards
compatible change, and we can now use unittest2's latest version,
which we were previously unable to due to unittest2 using a newer
version of six.
Merge branch 'upgrade-six' into develop

* upgrade-six:
  Upgrade versions of six/unittest2
Fix endpoint config for emr

These are based on endpoint prefix.  This means that we were
not creating the proper endpoints for emr, which would fail
SSL cert validation in py2.6.  This was caught by an integration
test that was recently added that happened to use EMR.
Merge branch 'fix-emr-endpoints' into develop

* fix-emr-endpoints:
  Fix endpoint config for emr
Fix base64 serialization in JSON protocol

This includes adding additional protocol tests for blob serialization.
These were no tests for blobs in the json protocol input tests.

Fixes #385, aws/aws-cli#1033
Switch kinesis integ tests over to client interface
Add integ test for blob serialization in json protocol

This also included adding a waiter config for kinesis.
Merge branch 'fix-json-serialization' into develop

* fix-json-serialization:
  Add integ test for blob serialization in json protocol
  Switch kinesis integ tests over to client interface
  Fix base64 serialization in JSON protocol
Fix failing integ test on py3
Update the service model for several services
Bumping version to 0.77.0
Merge branch 'release-0.77.0'

* release-0.77.0:
  Bumping version to 0.77.0
  Update the service model for several services
  Fix failing integ test on py3
  Add integ test for blob serialization in json protocol
  Switch kinesis integ tests over to client interface
  Fix base64 serialization in JSON protocol
  Fix endpoint config for emr
  Upgrade versions of six/unittest2
  Fix integ test failure by specifying a region
  Fix regression for supported timestamp formats