Use cmd table names for event names

The underlying change was to be able to pull in the `s3api` examples (https://github.com/jamesls/aws-cli/commit/597da6f07bc19d2d92997611f4d9bd0cd735479a) which required one high level change:

* The path used to look for example files uses the name in the cmd table (in this case `s3api`).  It was previously looking for a path like `examples/s3/put-object.rst` but it needed to be `examples/s3api/put-object.rst`.

Part of this change includes using the command table for the help command titles so that when you run `aws s3api help` you'd see the name of the command listed as `s3api` instead of `s3`.

This also fixes the case where the endpoint prefix does not match the name in the command table.  An example of this is the cloudwatch vs. monitoring difference where the examples are in the `examples/cloudwatch` dir.  As a side-effect, this also fixes #233.

Also note that this PR is branched off of #249, so it will include that diff as well until that PR is merged.

cc @garnaat @toastdriven