Fix for #1381: Fail test with warning if the developer does not make the...

...ir test inherit from PHPUnit_Framework_TestCase or PHPUnit_Framework_TestSuite
The second sentence should be removed.  I think we can also remove the leading "The":

```
Class "%s" does not inherit from PHPUnit_Framework_TestCase or PHPUnit_Framework_TestSuite.
```
Given above mentioned condition change, we can shorten it further and make the error match the condition in natural language:
```
Class "%s" is not a PHPUnit_Framework_Test.
```