chore: use greater than for npm engine

Using a caret means that it wants npm 3 and not greater than npm 3

package.json

@@ -65,6 +65,6 @@
   },
   "main": "dist/MaterialColorPicker.js",
   "engines": {
-    "npm": "^3.0.0"
+    "npm": ">=3.0.0"
   }
 }