Add Nanum Gothic Coding font for Korean support

PyTagCloud is awesome, but it can be even more awesome with multilingual support.

I have added a free font called "Nanum Gothic Coding" to make it possible to build a Korean tag cloud with PyTagCloud. You can see an example [here](https://github.com/e9t/konlpy/wiki/Examples#%EA%B5%AD%ED%9A%8C-%EB%B0%9C%EC%9D%98-%EC%9D%98%EC%95%88-%EC%9B%8C%EB%93%9C-%ED%81%B4%EB%9D%BC%EC%9A%B0%EB%93%9C-%EA%B7%B8%EB%A6%AC%EA%B8%B0).

![wordcloud](https://cloud.githubusercontent.com/assets/1205890/3240670/e79011fc-f12f-11e3-8d36-263235c84a55.png)