Multiple event listeners in element extension causes an error

[Jabher]

http://jsfiddle.net/s91o0w7m/
Something like

Vue.extend({
events: {broadcast: 'parser1'}
}).extend({
events: {broadcast: 'parser2'}
})

fails during init.
This happens due to https://github.com/yyx990803/vue/blame/master/src/util/merge-option.js#L174
parent is not an array, however it is expected to be an array.

[yyx990803]

Thanks!