[TEST] Reconfigure regex parsing/matching

Switched back to forward slash delimeters, but now includes extra
escaping for forward slashes.

There were just as many problems with the alternative delimeter, so
it seems that escaping is nescessary no matter which one is chosen.
Might as well use the default :)

tests/Elasticsearch/Tests/YamlRunnerTest.php

@@ -133,10 +133,11 @@ private function assertFalsey($value)
     private function assertRegex($pattern, $actual) {
         $pattern = trim($pattern);
 
-        // PHP doesn't like unescaped forward slashes, switch to a new delimeter
-        // to make life easier
+        // PHP doesn't like unescaped forward slashes
         $pattern = substr($pattern, 1, strlen($pattern)-2);
-        $pattern = "%$pattern%mx";
+        $pattern = str_replace('/', '\/', $pattern);
+        $pattern = "/$pattern/mx";
+        echo "\n> pattern: $pattern\n";
         ob_flush();
         $result = preg_match($pattern, $actual, $matches);
         $this->assertEquals(1, $result);