Resolving issue #51

Fixing the following warning (by using scala.reflect.ClassTag) gives compilation error with scala 2.9.3 

[warn] .../cassovary/src/main/scala/com/twitter/cassovary/util/SmallBoundedPriorityQueue.scala:22: type ClassManifest in package reflect is deprecated: Use scala.reflect.ClassTag instead
[warn] class SmallBoundedPriorityQueue[A](maxSize: Int)(implicit m: ClassManifest[A], ord: Ordering[A]) {
[warn] one warning found

I have not included the changes related to above warning in this PR...
Should the change(s) be made?