IAM Profile Support for Created instance

This adds the IAM role named in the config to the created instance. 

Works just like knife-ec2 --iam_instance_profile: 
https://github.com/opscode/knife-ec2/blob/master/lib/chef/knife/ec2_server_create.rb#L54

This should close #18 and #32 as well. Note: #32 works too but in a not so clean way imo.

The reason for this is using fog as a chef_gem to attach ebs drives and update route53 domains in the context of a chef run.

Let me know if you have any questions.