Improve overlap of lines in network graph

### Before

![improve-overlap-lines-befoer](https://f.cloud.github.com/assets/72138/111228/68d84984-6aed-11e2-93c9-a37664784be5.png)

### After

![improve-overlap-lines-after](https://f.cloud.github.com/assets/72138/111231/7179b7c6-6aed-11e2-9d27-9b020d00c6e6.png)