Update the signature of IProgress<T> for .NET 4+ (fixes #26)
Use default(VoidResult) instead of null where applicable
Merge pull request #35 from sharwell/typed-null

Use default(VoidResult) instead of null where applicable
Merge pull request #34 from sharwell/iprogress-sig

Update the signature of IProgress<T> for .NET 4+
Split TestTaskBlocks into separate files for Using and While tests
Split TestCoreTaskExtensions into separate files for Finally, Select, and Then tests
Merge pull request #39 from sharwell/split-tests

Split tests
Include additional documentation samples to relate extension methods to async/await behavior