New implementation of KeyTopper.

This implementation follows the algorithm of the paper
"Efficient computation of frequent and top-k elements in data streams."
It is a replacement of the ConcurrentKeyTopper implementation.

commit 2e345e5e3ad2dd8a1a969bc8afc99a06af405c8a
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Mon Apr 21 09:30:40 2014 -0400

    Final changes to new keytopper implementation.

commit bd83e5c9ac00eae2e40faedafca2f3105a9b1e73
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Fri Apr 18 23:51:00 2014 -0400

    Cleanup.

commit 38cb3e97db4d0244c7d90ff9cbda96fa443940a7
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Fri Apr 18 21:52:02 2014 -0400

    Hooray! Eliminate sort order improves performance.

commit 2c734a1378523605ccb20368988d02187ee8867a
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Fri Apr 18 20:46:51 2014 -0400

    Bugfix in keytopper performance tests.

commit 0f43395e75b926f11e0515e5a15502b2fc8b70f7
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Fri Apr 18 19:38:14 2014 -0400

    Cleanup.

commit 1c6ca5df100331ac9e8f8786edb74cd0b1a11c17
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Fri Apr 18 18:39:45 2014 -0400

    Adding AltKeyTopper implementation for comparison.

    Simple implementation is faster than complicated implementation.

commit ffdf97da0875a1e7adf219977fca7ca3c14f3065
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Fri Apr 18 10:57:50 2014 -0400

    Cleanup of KeyTopper continuation bytes test.

commit d0696abff43d4569def6b1d8fbab74cec90da5a5
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Fri Apr 18 10:36:28 2014 -0400

    Serialization unit tests for new KeyTopper.

commit 549d0df8e99732b60bdc3e146616b7e9e5aa5c36
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Fri Apr 18 09:47:07 2014 -0400

    Initial working commit of new implementation.

    Needs additional unit tests and performance tests.

commit 32bf313dbecabd9e65b137e1325cd4ece6b1db86
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Thu Apr 17 15:54:26 2014 -0400

    Initial working implementation.

    Have not implemented the codec or concurrency features.

commit 428baafc914c676b23269e62e5e831d07e363ee7
Author: Michael Spiegel <spiegel@addthis.com>
Date:   Thu Apr 17 11:08:14 2014 -0400

    Initial commit. Does not compile.
Merge pull request #76 from addthis/keytopper-fix-export

New implementation of KeyTopper.