Move the js module to a js_sys crate (#512)

* Move the `js` module to a `js_sys` crate

* Update js-sys tests to pass again

* Update binding_to_unimplemented_apis_doesnt_break_everything

Remove its dependency on the `js` module

* Update metadata for js-sys

* Fix the `closures` example

crates/js-sys/tests/all/SetIterator.rs

@@ -0,0 +1,97 @@
+#![allow(non_snake_case)]
+
+use project;
+
+#[test]
+fn entries() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(use_extern_macros)]
+
+            extern crate wasm_bindgen;
+            extern crate js_sys;
+            use wasm_bindgen::prelude::*;
+
+            #[wasm_bindgen]
+            pub fn entries(this: &js_sys::Set) -> js_sys::SetIterator {
+                this.entries()
+            }
+
+        "#)
+        .file("test.js", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                let set = new Set([8, 5, 4, 3, 1, 2]);
+                let wasmIterator = wasm.entries(set);
+                let nextValue = wasmIterator.next().value;
+
+                assert.equal(nextValue[0], 8);
+                assert.equal(nextValue[1], 8);
+            }
+        "#)
+        .test()
+}
+
+#[test]
+fn keys() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(use_extern_macros)]
+
+            extern crate wasm_bindgen;
+            extern crate js_sys;
+            use wasm_bindgen::prelude::*;
+
+            #[wasm_bindgen]
+            pub fn keys(this: &js_sys::Set) -> js_sys::SetIterator {
+                this.keys()
+            }
+
+        "#)
+        .file("test.js", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                let set = new Set([8, 5, 4, 3, 1, 2]);
+                let wasmIterator = wasm.keys(set);
+                let nextValue = wasmIterator.next().value;
+
+                assert.equal(nextValue, 8);
+            }
+        "#)
+        .test()
+}
+
+#[test]
+fn values() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(use_extern_macros)]
+
+            extern crate wasm_bindgen;
+            extern crate js_sys;
+            use wasm_bindgen::prelude::*;
+
+            #[wasm_bindgen]
+            pub fn values(this: &js_sys::Set) -> js_sys::SetIterator {
+                this.values()
+            }
+
+        "#)
+        .file("test.js", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                let set = new Set([8, 5, 4, 3, 1, 2]);
+                let wasmIterator = wasm.values(set);
+                let nextValue = wasmIterator.next().value;
+
+                assert.equal(nextValue, 8);
+            }
+        "#)
+        .test()
+}