Quadratic fitting for depth error

* add --csv option to estimate parameter from csv file
* add --model option to specify model to fit. now it supports linear and quadratic

![screenshot_from_2014-10-25 01 08 17](https://cloud.githubusercontent.com/assets/40454/4773467/057a1b94-5ba3-11e4-9289-d4be16766c55.png)
![screenshot_from_2014-10-25 01 36 09](https://cloud.githubusercontent.com/assets/40454/4773466/05754786-5ba3-11e4-9f44-31295830df76.png)