Document MySQL setup

PyMySQL is more difficult to install since its version 0.9 since it now depends
on *cryptography* lib, which in turns depends on OpenSSL and Python dev files.

See https://github.com/PyMySQL/PyMySQL/issues/697

CHANGELOG.rst

@@ -6,8 +6,16 @@ This document describes changes between each past release.
 2.1.1 (unreleased)
 ------------------
 
+Fixed
+=====
+
 - Regenerate translations (#338)
 
+Added
+=====
+
+- Document MySQL setup (#357)
+
 
 2.1 (2018-02-16)
 ----------------

docs/installation.rst

@@ -63,6 +63,22 @@ Once installed, you can start a test server::
 
 And point your browser at `http://localhost:5000 <http://localhost:5000>`_.
 
+Configure database with MySQL/MariaDB (optional)
+================================================
+
+Only required if you prefer MySQL/MariaDB over SQLite.
+
+1. Install PyMySQL dependencies. On Debian or Ubuntu, that would be::
+
+    apt install python3-dev libssl-dev
+
+2. Install PyMySQL (within your virtualenv)::
+
+    pip install 'PyMySQL>=0.9,<0.10'
+
+3. Create an empty database and a database user
+4. Configure :ref:`SQLALCHEMY_DATABASE_URI <configuration>` accordingly
+
 Deploy it
 =========
 
@@ -159,6 +175,8 @@ For example, use the following command to add more gunicorn workers::
 
     docker run -d -p 8000:8000 ihatemoney -w 3
 
+.. _configuration:
+
 Configuration
 =============