add a code of conduct to the JAWAD website

modeled after the JSConf code of conduct: http://jsconf.com/codeofconduct.html

@dabit3 this isn't ready to merge yet (i need to tweak the headline styles) What do you think about the direction i'm going with including the code of conduct in the front page?  Does it fit with how you want the site to look, etc.?

![screenshot-jawad-code-of-conduct-unstyled](https://cloud.githubusercontent.com/assets/12147/5480024/5bf9ca34-8608-11e4-9cd7-1128ee8637df.png)

after the look is nailed down, i'll message the mailing list to begin honing the code of conduct text itself, then we'll be ready to merge this onto the live site.