make react JSX transformer more generic and allow JSX comments - closes #841

test/fixtures/transformation/react/honor-custom-jsx-comment/actual.js

@@ -0,0 +1,8 @@
+/** @jsx dom */
+
+<Foo></Foo>;
+
+var profile = <div>
+  <img src="avatar.png" className="profile" />
+  <h3>{[user.firstName, user.lastName].join(" ")}</h3>
+</div>;

test/fixtures/transformation/react/honor-custom-jsx-comment/expected.js

@@ -0,0 +1,14 @@
+/** @jsx dom */
+
+dom(Foo, null);
+
+var profile = dom(
+  "div",
+  null,
+  dom("img", { src: "avatar.png", className: "profile" }),
+  dom(
+    "h3",
+    null,
+    [user.firstName, user.lastName].join(" ")
+  )
+);