Add install document.

INSTALL.md

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+Installing brutaldon
+====================
+
+Brutaldon is a perfectly normal Django app, so if you've ever installed a Django app, it should be straightforward. It will work either as a local application, or installed on a server.
+
+For either case, you will need Python 3 installed to start with, including pip.
+
+Common steps
+---------------------------------------------------------
+If you haven't already, you need to install [Pipenv][pe], a tool for managing Python virtual environments. 
+
+You can install it just with  `pip install pipenv`.
+
+[pe]: https://github.com/pypa/pipenv/
+
+Development or local install
+------------------------------------------------
+In the top brutaldon directory, run `pipenv install`. This will install all the dependencies. Then run `pipenv run python ./manage.py migrate`. That will create a SQLite database the application needs. Then run `pipenv run python ./manage.py migrate`. That will start a local server on http://localhost:8000/.
+
+Point your browser to that address and log in to your instance. You will have to log in with the alternate (username and password) method. 
+
+Server installation
+----------------------------------------
+This will depend on your server setup, and you should consult [Deploying Django][dd]. Be sure to read the [Deployment checklist][dc], because some things in it are security critical. 
+
+One common step would be to install dependencies like this: `PIPENV_VENV_IN_PROJECT=1 pipenv install`. This will install dependencies within the project folder.
+
+Then edit brutaldon/settings.py. You definitely need to change the values of SECRET_KEY and ALLOWED_HOSTS.
+
+I installed brutaldon with Apache and mod_wsgi. If you installed brutaldon in /usr/local/share/, you'd add config lines something like this to the virtual host brutaldon is installed in.
+
+```
+Alias /brutaldon/static /usr/local/share/brutaldon/brutaldon/static
+<Directory /usr/local/share/brutaldon/brutaldon/static>
+    Require all granted
+</Directory>
+
+WSGIScriptAlias /brutaldon /usr/local/share/brutaldon/brutaldon/wsgi.py
+WSGIDaemonProcess brutaldon python-path=/usr/local/share/brutaldon python-home=/usr/local/share/brutaldon/.venv
+
+<Directory /usr/local/share/brutaldon/brutaldon>
+    <Files wsgi.py>
+        Require all granted                                                      </Files>
+</Directory>
+```
+
+Be sure you serve the entire site over https only.
+
+[dd]: https://docs.djangoproject.com/en/2.0/howto/deployment/
+[dc]: https://docs.djangoproject.com/en/2.0/howto/deployment/checklist/