Nuorder

* Support Python 3.7

* Make the `data` arg optional for POST/PUT requests
* Previously we returned a "request error" when response from NuOrder couldn't be processed as JSON. Instead of `{"request_error": [response text]}` we're now returning the more descriptive `{"response_status_code": [HTTP status code], "response_text": [response text], "json_decode_error_details": [JSONDecodeError details]}`, or `{}` if there was no response body (which of course would fail to parse as JSON).

* Refactor to use class, for easier repeated access
* New CLI named `interact`, for more easily interacting with the nuorder API,
using the IPython REPL.
* `requests` is now the only dependency in the base package. `argh` and `termcolor` are now installed by issuing `pip install nuorder[cli]`
* Limit config initialization to CLI, to enable programmatic usage

* Support gzipped data transfers for POST and PUT requests with the -g flag
* List python 3.6 as supported

* Initial version