Email Settings Documentation 

Email settings documentation pulled from 
http://projects.theforeman.org/projects/foreman/wiki/Email_configuration

and formatted in MarkDown.  I put it in Section 3.5 after settings/config.yml
@ntent-ashton Can you remove this line? It seems to cause problems, it's being interpretted as a new header:

![foo](https://cloud.githubusercontent.com/assets/429763/4683551/af7acc64-5627-11e4-84b5-df8c565d0537.png)