Added

- support for web worker. #11

Changed
- throw error if input type is incorrect.
- prevent webpack to require dependencies.

tests/worker.js

@@ -0,0 +1,12 @@
+var imported = false;
+onmessage = function(e) {
+  if (imported) {
+    postMessage(md5(e.data));
+    if (typeof exports !== 'undefined') {
+      imported = false;
+    }
+  } else {
+    imported = true;
+    importScripts(e.data);
+  }
+}