Add globbing support like a native phpunit

Add support phpunit.xml configurations like this:
```xml
    <testsuites>
        <testsuite name="Project Test Suite">
            <directory>../src/*/Bundle/*Bundle/Tests</directory>
        </testsuite>
    </testsuites>
```
Isn't this what ```isGlobRequired``` is for?

If you would move this check for a realpath to ```isGlobRequired()``` and call it from here, you could remove the conditional switch from ```getSuites()``` and always call ```getSuitePaths()``` (which will then call isGlobRequired and only return one element for the default case).
That would also reduce the high complexity from ```getSuites()``` (while, foreach, if, foreach).