import implementation of Fsub from the Coq tutorial of UPenn

taken from 'https://www.cis.upenn.edu/~plclub/popl08-tutorial/code/index.html'

coq-Fsub/_CoqProject

@@ -0,0 +1,13 @@
+-R . Fsub
+AdditionalTactics.v
+FSetDecide.v
+FSetNotin.v
+ListFacts.v
+FiniteSets.v
+Atom.v
+Metatheory.v
+Fsub_Definitions.v
+Fsub_Infrastructure.v
+Fsub_Lemmas.v
+Fsub_Soundness.v
+