Add missing impl to EdgeIndex
diff --git a/src/graph_impl/mod.rs b/src/graph_impl/mod.rs
index dbedd35..29dfb87 100644
--- a/src/graph_impl/mod.rs
+++ b/src/graph_impl/mod.rs
@@ -158,6 +158,10 @@
     }
 }
 
+impl<Ix: IndexType> From<Ix> for EdgeIndex<Ix> {
+    fn from(ix: Ix) -> Self { EdgeIndex(ix) }
+}
+
 impl<Ix: fmt::Debug> fmt::Debug for EdgeIndex<Ix>
 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {