Rename "output" arg to "job_output"

The CLI has an "output" option already which shadows this arg.
Merge branch 'ets-create-job-rename' into develop

* ets-create-job-rename:
  Rename "output" arg to "job_output"
Readd support for proxies from env vars

This is a regression when we upgraded to requests 1.x.
A proxy can be figured via the normal env vars used by
requests.  We now forward the `proxies` arg along
to the `send()` method of the request session.

Part of this change included refactoring the endpoint classes
to remove some duplication.  I've also added unit tests for
these changes.
Merge pull request #32 from jamesls/readd-proxy-env

Readd support for proxies from env vars
Fixing a bug in the JSON service description for OpsWorks.
Merge branch 'develop' of github.com:boto/botocore into develop
Fix opsworks unit test.
Bumping version number.