Publish release notes for v0.2

Update README.md with new site url

Add release notes into NuGet package and update project url

Avoid depending on System.Memory on frameworks other than .NET Standard 2.0

Skip ChaCha SSE2 tests when SSE2 is not supported

Bump package version to 0.2.0

Merge master into 'default'

Update docs for API changes

Add a benchmark for the SuffleInPlace extension method

Remove IRng.Sample(IDistribution<T>) extension methods due to performance issues

These extension methods were provided as a possibly more convenient way to
sample a distribution, allowing the developer to use `rng.Sample(dist)` instead
of `dist.Sample(rng)`. Unfortunately, these methods have a hidden performance
penalty. The extension method operating on non-generic IDistribution is up to
4x slower than directly using dist.Sample, and the generic extenion method is
up to 2x slower (with the added annoyance of having to specify every type
parameter).

Remove IPortableDistribution implementation from Single and Double UnitInterval distributions

Mark methods and properties as 'Pure' where appropriate

Remove readonly modifier from BlockBuffer32 field, ensuring that changes will be persisted even if TBlockRng is a struct

Shuffle around comments on confidence intervals and z-scores and remove the confidence interval property, since only the z-score is ever used

Make various minor style adjustments to make ReSharper happy

Move UnitInterval distributions into separate namespace and group into nested classes

Reduce the ClusterTest target time

Implement RandomShim with UnitInterval.ClosedOpenDouble instead of a UniformDistribution

Use parameterized XUnit Theory tests instead of Fact tests where appropriate

Fix failing Test in ThreadLocalRngTests