Add Twiter case.

The case contains strange trippled array of doubles (double[][][]).
Change the name of ToString method to Describe in IResultData.

Because the method ToString is implemented by object itself, the
method ToString required by the interface seems to be improper.
Clean up solution and projects settings.

In order to always have Runner set as the startup project, the
solution has to list it as the first project in the solution.
Update the README.md with current benchmarks.