Created main project
Added IcoAttribute and GreaterThanAttribute
Added YearOffsetAttribute
Formatting changes
Added DateOffsetAttribute
Ignoring packages folder
Changed logic to use negative values
Using string timespan specifications
Added sample model editing form
Enabled NuGet package restore
Enabled automatic NuGet package generation
Added Markdown CSS for Web Essentials
Specified attribute usage options
Updated README.md with usage info.