Allow describing stack parameters/outputs

In order to support parameterized stacks,
add display of stack parameters.

Also out display of stack outputs as they are related.
Merge branch 'add_stack_description_command' of https://github.com/nightlyone/gocloud into nightlyone-add_stack_description_command

* 'add_stack_description_command' of https://github.com/nightlyone/gocloud:
  Allow describing stack parameters/outputs

Conflicts:
	aws/cloudformation/describe_stacks.go