Add file for Deployment class

ticket:2
Basic Deployment class

ticket: 2
List deployments

- TODO: Find a repo to test against
Add ability to create a deployment
Use proper headers
Fix construction of iter_deployments iterator
Add repr to Deployment class
Add integration test for iter_deployments
Add integration test for Repository#create_deployment
Add iter_statuses and DeploymentStatus
Add iter_statuses and create_status to Deployment
filter on py3k is different
Fix test helper once and for all
Add Deployment classes to the Repos section
Merge pull request #190 from sigmavirus24/feature-deployments-api

Deployments API
Fix minor doc bug on Repository.iter_issues

I saw the `sort` parameter in Github's documentation, but was wondering where it was in github3.py.  It turns out it's there, both supported and documented, but the doc line was mistakenly merged into the previous line, which makes it easy to miss.

Now it should be more hunky-dory.
Merge pull request #214 from xiongchiamiov/develop

Fix minor doc bug on Repository.iter_issues