Cromwell-tools

- Fix a bug with the service account key that prevents users from using any authentication methods.
- Fix a bug with `/validate` command in CLI.
- Fix a bug with `/health` endpoint in API.
- Improve the output of the CLI commands.
- Update the documentation, quickstart Jupyter notebook, and docstrings.
- Update the authentication dependency from the deprecated `oauth2client` to `google-auth`.
- Allow no-auth with Cromwell.

Changes:
- A breaking refactoring work on both the CLI and API.
- More sophisticated unit tests.
- Support both Python2 and Python3, having tests run on both versions.
- Updated ReadMe file and docstrings.
- For `/submit` endpoint, we support both path to the file and file contents as inputs now.
- We have a quickstart example Jupyter Notebook now.
- Update requests to avoid security issues.
- Fix API calls in CLI.
- We have accessory tools with cromwell-tools, such as the workflow monitoring script.
- Other slight improvements and bug fixes.

**Note**: from this version we will start to publish this package on PyPI.

- Add a new function to query workflows.
- Add a new function to release workflows from status `On Hold` to `Submitted`.

- Add on_hold parameter to start_workflow
- Add workflow validation capability
- Add Sphinx autodoc and readthedocs hook
- Bugfix: Allow workflows without labels to be executed
- Bugfix: Fix docker container build issues

Use officially blessed package `setuptools_scm` to control the version of Cromwell-tools, add `__version__` attribute in the package level.

Add option to use Cromwell-as-a-Service

Update the functions that make requests to Cromwell to send a bearer token generated from the CaaS key if the key is provided, otherwise use the username and password.