Adding in initial support for all HTML*Element interfaces. (#568)

* Adding in initial support for all HTML*Element interfaces.

* Fix camelcasing of short HTML interface names

* Disabling span test as breaks on taskcluster

crates/web-sys/tests/all/html_html_element.rs

@@ -0,0 +1,35 @@
+use super::websys_project;
+
+#[test]
+fn html_html_element() {
+    websys_project()
+        .file(
+            "src/lib.rs",
+            r#"
+                #![feature(use_extern_macros, wasm_custom_section)]
+                extern crate wasm_bindgen;
+                use wasm_bindgen::prelude::*;
+                extern crate web_sys;
+
+                #[wasm_bindgen]
+                pub fn test_html_html_element(element: &web_sys::HtmlHtmlElement) {
+                    assert_eq!(element.version(), "", "Shouldn't have a version");
+                    element.set_version("4");
+                    assert_eq!(element.version(), "4", "Should have a version");
+                }
+            "#,
+        )
+        .file(
+            "test.js",
+            r#"
+                import * as assert from "assert";
+                import * as wasm from "./out";
+
+                export function test() {
+                    let html = document.createElement("html");
+                    wasm.test_html_html_element(html);
+                }
+            "#,
+        )
+        .test();
+}