Update program to eliminate use of NUnit 2.2.10

[CharliePoole]

NUnitResults uses NUnit 2.2.10 assemblies to create test results from the input xml file. This limits its ability to deal with result files created by recent versions of NUnit. There are two optional ways to deal with this:

1. Use a later version of NUnit
2. Don't use NUnit at all so there is no longer a dependency.

The second approach is preferable and should be tried first.

Originally https://bugs.launchpad.net/nunit-results/+bug/491548