Enable Matviz to require dax and state we need the tbb backend.
Implement a parallel histogram algorithm.
Correct issue with linking to tbb.
Correct case insensitive find for Dax.
Correct not using the first value of each tasks histogram subset.
Turn Dax off by default.
Merge pull request #6 from robertmaynard/dax-histo

Implement faster serial and parallel versions of histogram.