Extensions to cfn tool

Hi, I made some extensions to the cfn tool to support my workflow with troposphere.

The only change to existing behavior is the --create operation now waits for the stack creation to complete.  It tails along the stack event log waiting for a completion event, printing out events along the way.  The exit code of the tool will be nonzero if the creation failed.

I also added --delete and --update operations that behave in a similar way.

I also made the tool automatically render .py templates into json before sending to AWS.

Finally, I added a --capability flag which is necessary to create stacks if they use IAM capabilities.

Is troposphere interested in any of this work?

Thanks for the cool project!