The size of CloseButton presented in MetroTabItem will be changed proportionately considering its HeaderFontSize. In addition, an example has been added into MetroDemo project.
Support for .NET 4.5.
Remove MetroTabItemCloseButtonFontSizeConverter.
Merge pull request #1310 from oloopy/MetroTabItem-CloseButtonSize

The size of CloseButton in MetroTabItem will be changed proportionately.