add -doc-source-url option

### before

![before](https://f.cloud.github.com/assets/389787/71818/c65ee626-5ff8-11e2-8439-7d196eaf6d1e.png)


### after

![after](https://f.cloud.github.com/assets/389787/71810/8f43954c-5ff8-11e2-90ad-5dd8da0908dc.jpg)