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