Adding the EiffelStudio .gitingore file.

EiffelStudio is a framework, toolchain and editor to develop application using the Eiffel language.

See: http://www.eiffel.com/

and: http://dev.eiffel.com/

When an Eiffel project is compile with the EiffelStudio compiler, every generated files are put in the "EIFGENs" directory. So this is the directory to ignore.

If you have any question, don't hesitate to ask.