generated Feature tests should use TestCase instead of PHPUnit's

Author: Mulkave

src/Generators/stubs/feature-test.stub

@@ -1,7 +1,7 @@
 <?php
 namespace {{namespace}};
 
-use PHPUnit_Framework_TestCase as TestCase;
+use TestCase;
 use {{feature_namespace}};
 
 class {{testclass}} extends TestCase