Vendor dependencies for 0.3.0 release

vendor/petgraph/src/util.rs

@@ -0,0 +1,16 @@
+use std::iter;
+
+pub fn enumerate<I>(iterable: I) -> iter::Enumerate<I::IntoIter>
+where
+    I: IntoIterator,
+{
+    iterable.into_iter().enumerate()
+}
+
+pub fn zip<I, J>(i: I, j: J) -> iter::Zip<I::IntoIter, J::IntoIter>
+where
+    I: IntoIterator,
+    J: IntoIterator,
+{
+    i.into_iter().zip(j)
+}