This more reliably ensures that the user has up-to-date dependencies (e.g. without it, a
beta version of a package like Willow or modelcluster won't get installed if the user has
a stable version already installed)
* Removed requirements-dev.txt
* Added dependencies to setup.py using the extras_require option
* Updated the documentation to use pip instead of setup.py develop
* Updated .drone.yml to reflect updated installation
The Elasticsearch tests now depend on an environment variable being set so we can safely install elasticsearch-py without Wagtail automatically assuming Elasticsearch is installed and running the tests.
This makes developer setup slightly easier, but also opens up the possibility for running some of the ES tests that don't depend on a running ES instance.
All `.. code::` instances have been changed to use `.. code-block::`,
and have been properly formatted. The syntax names have been normalised,
so all django templates use the `html+django` syntax, shell commands use
`sh`, and plain text uses `text`.
* State the requirement for Node.js up-front (since it's required by everyone, not just front-end devs)
* Point to vagrant-wagtail-develop instead of making people set up a Vagrant instance manually
* No need to fiddle with python paths via local.py - 'setup.py develop' handles that
* Skip instructions for virtualenvs (anyone who decides against the Vagrant route is expected to know how to use them)
