Includes many performance improvement, thank you @udaken
- Implement ZString.Concat works as same as string.Concat on collection types #19, thanks @piti6
- Add some BCL-like methods to StringBuilder #20
- Add StringBuilder.AppendJoin #21
- Make throw NestedStringBuilderCreationException on nested StringBuilder creation. #23
- Removes allocation when using IntPtr and Nullable. #24
- Fix Utf8PreparedFormat #26
- Improved performance of StringBuilder.AppendFormat #27