added skeleton test for adding nodes, and updated test suite
ensuring that --ips has a value passed to it
making sure that file specified via --ips exists
validating yaml given to ensure it actually is valid yaml
also making sure ips.yaml file isn't just an empty file
not allowing users to add master nodes
verifying that local ssh key can log into each new machine to add
amended appcontrollerclient to remotely spawn new nodes, and changed add-nodes to pass data in the right format to it
renamed add_nodes to add_instances
now accepting add_to_existing as a flag to add-keypair, and added more test case coverage for it
added test/code to support only adding key to one node
extracted expect_script to a constant, since it's location never changes
fixed how we generate ssh keys in xen deployments
added new tool, add-instances, to dynamically add nodes (in xen so far)
changed ssh options to not check the remote host against our currently known hosts, fixing issue #53
renamed appscale-add-instances test cases to match lib name
changed name of public key in tests to reflect what we actually call it
clarified documentation on add-instances methods
printing success message for add-instances, instead of printing nothing
documented globals we use for add-instances