Support parenthesis in the covers annotation

[christeredvartsen]

With this PR the covers annotation can have parenthesis after method names:

<?php
class SomeTest extends PHPUnit_Framework_TestCase {
    /**
     * @covers SomeClass::test()
     */
    public function testSomething() {

    }
}

Without this support the error message is quite misleading as it says:

Trying to @cover not existing method "SomeClass::test()".

when the test() method clearly exists.

I'm not too sure about how to go about testing this, so I changed some of the covers annotations in the CodeCoverageTest.php test case to include the supported ways of using the parenthesis.