Adding examples to the documentation.

Created an example of each of the shouldly features that was listed in the readme.md. The method "ShouldBeCloseTo" seems to be no longer supported, so I removed it. "ShouldNotContainKeyAndValue" seems to have been replaced with "ShouldNotContainValueForKey".

Still a lot more room for improvement, but hopefully this will be a substantial improvement to the existing documentation. Preview - https://github.com/chaitanyagurrapu/shouldly/tree/documentation_with_examples