Initial Support for Work items V2 API
 Support for V2 in createWorkItem
 bumped default API version to 1.0-preview.1
 Improved response parsing, it was failing if an error was returned
Merge pull request #20 from tspascoal/master

Make versioning API less ambiguous
Updating README
Fixing failing tests
Bumping version number
Updating README
Support HTTP proxies in tests
Support for work item API changes in version 1.0-preview.1
  Still compatible with 1.0-preview.1
  Fixed unit V1 unit tests
  Added unit tests for V2
Support for V2 changes
 work item methods support both V1 and V2
 added new methods only available in V2