Fall back to a configuration file if role description does not contain config token.

[renaudhager]

Keymaker will fall back on a config file if there is no config token present in role description.
See issue #33

[kislyuk]

Thanks for your contribution!

The overall idea here is great, but before this PR can be merged, it must:

• Use a standard or conventional file format and location (such as /etc/keymaker/config.yml). The only reason I used non-standard markup in the role description is that standard JSON/YAML/etc. markup characters are not allowed there.
• Use fully correct English in complete sentences in the documentation
• Conform to PEP-8.

[quagly]

I also only use cloudformation for role/instance profile creation and cloudformation does not support descriptions. config file seems like a reasonable approach, but I also like the idea of managing everything from within IAM. I wonder if role path may be a better option. /keymaker/... I am just getting started with keymaker and haven't implemented groups yet. When I require groups I may try this branch or try to use role path.