Added a link to the Contains() chapter to the index
Added documentation for string.Contains(string, StringComparison)
Added IsNullOrEmpty() and IsNullOrWhiteSpace() to the ToC
Added IsNullOrWhiteSpace() documentation
Added IsNullOrEmpty() documentation
Fixed formatting
Added documentation about the Truncate() extension method
Added a link to the page for .NET's string class on MSDN
Fixed link to FormatWith() heading
Fixed link
Created String extension methods (markdown)