Fix for word search exercise (#624)
Fix for word search exercise (#624)

* Fixed up template signature
wordsToSearchFor should be a string array, not a string
This matches the tests, and makes semantic sense
robkeim/xcsharp,ErikSchierboom/xcsharp,exercism/xcsharp,ErikSchierboom/xcsharp,exercism/xcsharp,robkeim/xcsharp