Conform to PSR-2, add Composer/PHPUnit configs

I've removed the two new exercises and squashed this into one commit, this PR reformat to PSR-2 standards.

The classes are now autoloaded with the phpunit.xml and composer.json provided. (This is done using Composer's autoloader)

The make file has been updated so only the tests are rewritten to the tmp dir and they are modified on the way to not skip tests and to require in the classes needed so it doesn't require an autoloader. (I'm sure this can be done in a nicer way as this is a bit hacky)

I am unsure how the CLI tool provides files, is it possible that when fetching PHP exercises that the composer.json & phpunit.xml are provided as well as perhaps a language specific README? That way when a user came to do some PHP exercises they would have a standard quick and easy way to get PHPUnit and the tests running. e.g:

    % curl -sS https://getcomposer.org/installer | php
    % php composer.phar install
    % php vendor/bin/phpunit [Exercise]

Let me know any problems/improvements and I'll work on it.

I haven't really looked too much at these exercises, I just ran autoformat against them. What about if the cast was removed as it shouldn't be needed anyway?

    $array = array_reverse(str_split($decimal));

I would even combine that to:

    public function __construct($decimal = '')
    {
        $this->digits = array_map('intval', array_reverse(str_split($decimal)));
    }

PSR-1/2 doesn't seem to care about the space between the cast, I couldn't find an example in the standards and CodeSniffer and PHPStorm rulesets do not point it out.