feat(input): add input type=range support

Bind model of <input type="range"> to number (like <input type="number">) rather than string. Range inputs represent numerical values; therefore, a numerical binding makes more sense than a string binding.

Closes angular#1189, angular#5892

Author: Tyler Eich

src/ng/directive/input.js

@@ -159,6 +159,7 @@ var inputType = {
       </doc:example>
    */
   'number': numberInputType,
+  'range': numberInputType,
 
 
   /**