Script to run install sequence on deploy.

Performs a self-update of composer.phar and then installs the non-dev
dependencies. Also generates the required (optimised) autoloader.

Includes update to latest version of composer.phar and packages in
composer.json.
Include file to quickly set testing environment variables.
Correctly ignore testing output.
Send code coverage results to Scrutinizer for analysis.
Include information explaining Sinn Fein MPs not taking their seats.