Vendor dependencies

Let's see how I like this workflow.

vendor/cassowary/tests/common/mod.rs

@@ -0,0 +1,35 @@
+use std::collections::HashMap;
+use std::cell::RefCell;
+use std::rc::Rc;
+
+use cassowary::Variable;
+
+#[derive(Clone, Default)]
+struct Values(Rc<RefCell<HashMap<Variable, f64>>>);
+
+impl Values {
+    fn value_of(&self, var: Variable) -> f64 {
+        *self.0.borrow().get(&var).unwrap_or(&0.0)
+    }
+    fn update_values(&self, changes: &[(Variable, f64)]) {
+        for &(ref var, ref value) in changes {
+            println!("{:?} changed to {:?}", var, value);
+            self.0.borrow_mut().insert(*var, *value);
+        }
+    }
+}
+
+pub fn new_values() -> (Box<Fn(Variable) -> f64>, Box<Fn(&[(Variable, f64)])>) {
+    let values = Values(Rc::new(RefCell::new(HashMap::new())));
+    let value_of = {
+        let values = values.clone();
+        move |v| values.value_of(v)
+    };
+    let update_values = {
+        let values = values.clone();
+        move |changes: &[_]| {
+            values.update_values(changes);
+        }
+    };
+    (Box::new(value_of), Box::new(update_values))
+}