Vendor dependencies

Let's see how I like this workflow.

vendor/rand/benches/distributions/exponential.rs

@@ -0,0 +1,18 @@
+use std::mem::size_of;
+use test::Bencher;
+use rand;
+use rand::distributions::exponential::Exp;
+use rand::distributions::Sample;
+
+#[bench]
+fn rand_exp(b: &mut Bencher) {
+    let mut rng = rand::weak_rng();
+    let mut exp = Exp::new(2.71828 * 3.14159);
+
+    b.iter(|| {
+        for _ in 0..::RAND_BENCH_N {
+            exp.sample(&mut rng);
+        }
+    });
+    b.bytes = size_of::<f64>() as u64 * ::RAND_BENCH_N;
+}