NFLabs/zeppelin — pull request #92 by Leemoonsoo (2014-09-15 22:34:15+00:00)
Title: Pie chart 

Here is initial pie chart implementation.

It works well except for changing pie chart <--> other chart raise some error, like
```
Error: Invalid value for attribute transform="translate(NaN,NaN)" d3.js:596
Error: Invalid value for attribute d="M0,-84A84,84 0 1,1 NaN,NaNL0,0Z"
```

In progress ...