Add color AZ and Flavor output to ec2 server list
Removing black option for unknown flavor to avoid problems on dark backgrounds
Merge pull request #150 from opscode/adamed-knife-342

KNIFE-342: Include AZ in output and colorize flavor column for easy reading.
it's now possible to specify an AWS credential file instead of access/secret keys
Address code review comments

Error handling logic is easier on the eyes
Added file format reminder in comments
add documentation
Merge pull request #153 from opscode/adamed-knife-294

KNIFE-294: Use credential file to specify access/secret keys
Update README.md

Fixed alignment issue in documentation.