Vendor dependencies

Let's see how I like this workflow.

vendor/smallvec/src/specialization.rs

@@ -0,0 +1,19 @@
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Implementations that require `default fn`.
+
+use super::{Array, SmallVec, SpecFrom};
+
+impl<'a, A: Array> SpecFrom<A, &'a [A::Item]> for SmallVec<A>
+where
+    A::Item: Clone,
+{
+    #[inline]
+    default fn spec_from(slice: &'a [A::Item]) -> SmallVec<A> {
+        slice.into_iter().cloned().collect()
+    }
+}