mysql dependency

Nobody has claimed this yet.

In case anyone gets this error when running the pip install:
```
Collecting mysql-python==1.2.5 (from quark)
Downloading https://files.pythonhosted.org/packages/a5/e9/51b544da85a36a68debe7a7091f068d802fc515a3a202652828c73453cad/MySQL-python-1.2.5.zip (108kB)
100% |████████████████████████████████| 112kB 2.5MB/s
Complete output from command python setup.py egg_info:
sh: 1: mysql_config: not found
Traceback (most recent call last):
File "", line 1, in
File "/tmp/pip-build-3MdNFi/mysql-python/setup.py", line 17, in
metadata, options = get_config()
File "setup_posix.py", line 43, in get_config
libs = mysql_config("libs_r")
File "setup_posix.py", line 25, in mysql_config
raise EnvironmentError("%s not found" % (mysql_config.path,))
EnvironmentError: mysql_config not found

----------------------------------------
```
Installing this dependency on Ubuntu will fix it:

```
sudo apt-get install libmariadbclient-dev
```

The package is probably similar on other distros.

Not a qark error but thought it was worth logging in case others hit it. Might be worth adding to the README.

Start in the README and review the pip-install instructions alongside the reported mysql_config error. Document the Ubuntu libmariadbclient-dev dependency and note that equivalent packages may be needed on other distributions; done means a newcomer can find this prerequisite before installation fails.

Written by the indexing model from the issue text.