Removed the Omidyar Network logo and changed the Avina logo.


Removed the Omidyar Network logo from "Con Apoyo de" in page index.
Also the Avina logo was replaced for Avina Americas.

![avina americas change](https://cloud.githubusercontent.com/assets/660973/4568078/f0d6b256-4f36-11e4-8d89-d7ace3031dfc.png)
¿No deberíamos de alojar nosotros esta imagen?