Vendor dependencies

Let's see how I like this workflow.

vendor/wasm-bindgen/tests/std-crate-no-std-dep.rs

@@ -0,0 +1,29 @@
+//! This is a test that we can define items in a `#![no_std]` crate when
+//! `wasm-bindgen` is compiled itself with the `std` feature and everything
+//! works out just fine.
+
+#![no_std]
+
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+extern "C" {
+    fn test(a: &str);
+
+    type Js;
+    #[wasm_bindgen(constructor)]
+    fn new() -> Js;
+    #[wasm_bindgen(method, structural)]
+    fn init(this: &Js);
+}
+
+#[wasm_bindgen]
+pub struct A {}
+
+#[wasm_bindgen]
+impl A {
+    pub fn foo(&self) {}
+    pub fn bar(&mut self) {}
+}