Stop using PEAR version of PHPUnit. Use git cloning instead.

Closes #471 

It was harder than I expected, because last PHPUnit version which run on PHP 5.2 is [3.6.x](https://github.com/sebastianbergmann/phpunit/tree/3.6). And PHPUnit does not provide [phar packages](https://phar.phpunit.de/) for 3.6.x branch, so I had to use cloning the PHPUnit (and its dependencies) repositories and checking out last versions which support PHP 5.2.

Was failing on error when the class was not loadable