Support to show Github issue's label name and assignee

For examples:
* `label`
![2014-09-09 16 52 37](https://cloud.githubusercontent.com/assets/290782/4198220/70fe59b4-37f6-11e4-950e-fd62728c4f5a.png)

* `assign`
![2014-09-09 16 53 26](https://cloud.githubusercontent.com/assets/290782/4198221/73f90a60-37f6-11e4-90d7-6bc8fe53725b.png)


This PR requires the unreleased feature of Idobata.
Close #14