Work for underscore events

Quick fix for prop event names with underscores
i.e. `bounds changed` becomes `Bounds_changed` with current camelize, so prop name has to be `onBounds_changed`.
This fixes it so that the prop name will be `onBoundsChanged`

Author: andrewgouin

src/lib/String.js

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