probably this file isn't included in the lib pack from the EAQ thread.
if that mod also works on the newer versions of the forge then just install the newer one
it's more likely wont work i think, i guess there's no other option than trying to search this particular library manually and putting it in the right directory
did it already
download this: http://central.maven.org/maven2/org/scala-lang/scala-reflect/2.11.1/scala-reflect-2.11.1.jar
aand put it there: .minecraft\libraries\org\scala-lang\scala-reflect\2.11.1\
installing should work after