speedup initialization (#27)

When the coverage object is used from cache we do not need to add the config again.

We have over 3000 files it takes ~18sec to collect the file list. So this speed up the coverage run a lot.

Author: gimler

Diff for: c3.php

@@ -190,6 +190,8 @@ function __c3_factory($filename, $lock=false)
             } else {
                 $phpCoverage = unserialize(file_get_contents($filename));
             }
+            
+            return array($phpCoverage, $file);
         } else {
             $phpCoverage = new PHP_CodeCoverage();
         }