Change input mask character for alphanumeric to w.

Change docs for inputmask.
Fixes #237

docs/javascript.html

@@ -396,8 +396,9 @@ $('.inputmask').inputmask({
         <tbody>
           <tr><td>9</td><td>Number</td></tr>
           <tr><td>a</td><td>Letter</td></tr>
-          <tr><td>?</td><td>Alphanumeric</td></tr>
+          <tr><td>w</td><td>Alphanumeric</td></tr>
           <tr><td>*</td><td>Any character</td></tr>
+          <tr><td>?</td><td>Optional - any characters following will become optional</td></tr>
         </tbody>
       </table>
     </div>

js/inputmask.js

@@ -47,7 +47,7 @@
     definitions: {
       '9': "[0-9]",
       'a': "[A-Za-z]",
-      '?': "[A-Za-z0-9]",
+      'w': "[A-Za-z0-9]",
       '*': "."
     }
   }