Fix d3 data formmating for chart drawing

This PR fixes #261 and other chart drawing bugs by changing d3 data contents.(remove data duplication, fill missing values with 0)

Area chart before
![2014-12-30 12 52 52](https://cloud.githubusercontent.com/assets/8503346/5575664/588953c8-9027-11e4-8dd3-c989751ce79b.png)

Area chart after
![2014-12-30 12 51 27](https://cloud.githubusercontent.com/assets/8503346/5575668/7ed84868-9027-11e4-8c2c-a188fca8b857.png)

Line chart before
![2014-12-30 12 53 34](https://cloud.githubusercontent.com/assets/8503346/5575669/85ba4ea6-9027-11e4-9e4f-4e99a50edc96.png)

Line chart after
![2014-12-30 12 53 53](https://cloud.githubusercontent.com/assets/8503346/5575670/89ea88b0-9027-11e4-920c-3fd360c6b17f.png)