Add ability to upload features

[ghost]

Hi guys! I am working on a framework and have been using this to download features from AssertThat and upload run reports. Would you mind if I submitted a PR to add a function to upload features back to assertthat?

You would pass it a path to your feature files, it would loop through each .feature file in there and call
/rest/assertthat/latest/project/{projectId}/client/upload