Used Flask-RESTful for API

Closes #162
it should not be a problem because JsonProperty using ```json``` module for serialization,  so it is possible to use ```fields.Raw```. For example
![1](https://cloud.githubusercontent.com/assets/47926/5581291/a50dbd74-9068-11e4-90ad-d06c5a81abdc.png)
![2](https://cloud.githubusercontent.com/assets/47926/5581305/d20c1adc-9068-11e4-825e-66e34019a1e2.png)
![3](https://cloud.githubusercontent.com/assets/47926/5581295/b002c468-9068-11e4-9932-6b3c8dec63c3.png)