Markdown editor version 2.0

This PR solves #70 also I think supply our needs commented on #129.

Here a few screens with what is done:

- New look on the editor:
![screen shot 2014-04-04 at 5 10 50 pm](https://cloud.githubusercontent.com/assets/230476/2619948/d0a3ad10-bc36-11e3-93f7-da335b2cec7c.png)

- Image Upload:
![screen shot 2014-04-04 at 5 15 26 pm](https://cloud.githubusercontent.com/assets/230476/2619954/ec3e110a-bc36-11e3-8c70-7d45c59420c4.png)
![screen shot 2014-04-04 at 5 16 00 pm](https://cloud.githubusercontent.com/assets/230476/2619955/ec3f4304-bc36-11e3-965a-322585c2f24a.png)

- Markdown Previewer:
![screen shot 2014-04-04 at 5 16 46 pm](https://cloud.githubusercontent.com/assets/230476/2619967/0f90003c-bc37-11e3-8085-cdc8c33f9296.png)