add robots.txt

### What is the problem / feature ?

Robots were trying to hit the site for a robots.txt

### How did it get fixed / implemented ?

Added a view to server the robots.txt file

### How can someone test / see it ?

visit http://volunteer.apogaea.com/robots.txt

*Here is a cute baby animal picture for your troubles...*

![funny_rats_elllen_van_deelen_13_](https://cloud.githubusercontent.com/assets/824194/2625370/32cca5c2-bd91-11e3-92e7-c2e3868e40d8.jpg)