Added fix and unit test for queryContentRegexAssertion() method

[RalfEggert]

Solves issue for #32.

[weierophinney]

The concern I have with this approach is that the regex might match across content boundaries.

As an example, consider this markup:

<div>foo</div>
<div>bar</div>

and then the following assertion:

$this->assertQueryContentRegex('div', '/foobar/');

The above, with the change you suggest here, would be a false positive.

I'd suggest doing the regex in the loop itself:

$found = false;

foreach ($result as $node) {
    if (preg_match($pattern, $node->nodeValue)) {
        $found = true;
        break;
    }
}

if (! $found) {
    throw new PHPUnit_Framework_ExpectationFailedException(/* ... */);
}

$this->assertTrue($found);

This approach will resolve the issue you reported in #32, while ensuring we
don't get false positives due to boundary issues.

[RalfEggert]

@weierophinney

I added another test case to handle unexpected false positives and added for solution. I had to tweak it a little otherwise the exception message had to actual content to output. I hope that tweak is ok.

[weierophinney]

Thanks, @RalfEggert! Cherry-picked to master, for release with 3.0.2.