Fix Problem wifth camelcase _

i have a problen listen onZoomChanged, i saw this function cant camelize when i have _ is only " ", i fix to solve the problem.
[#345](#345)

Author: misaku

src/lib/String.js

@@ -1,5 +1,5 @@
 export const camelize = function(str) {
-  return str.split(' ').map(function(word) {
+  return str.replace('_',' ').split(' ').map(function(word) {
     return word.charAt(0).toUpperCase() + word.slice(1);
   }).join('');
 }