Laniakea

* Small improvements to GCE and AWS integration

* Support for [Google Compute Engine](https://github.com/MozillaSecurity/laniakea/wiki/Google-Compute-Engine) has been added. It uses a Docker container declaration for spawning standard VMs and preemptible VMs.
* Module documentation for Cloud Providers has been moved to the Wiki.

* In certain circumstances a wrong availability zone is not caught directly by Boto. The requested spot instance is then set to state `failed` with status `bad-parameters`. This workaround fixes this issue by catching the status `bad-params` and canceling the reservation.

* Support default values for macros in UserData scripts

* Added support for Packet (Bare Metal)
* Dynamic module imports for cloud providers
* Removed obsolete UserData configurations
* Fixed PyLint issues
* Added Pipenv and Tox
* Improved setup.py (hopefully)
* Using now PyTest for the future rather than UnitTest
* Limit Azure to minimum requirements
* Hooked up TravisCI with Slack

<h4>Improvements</h4>

* Add azure support