Add Paging and Keep

Implemented list paging for secrets and orders along with updated unit tests

Added the command line tool, keep, which currently has all basic client functionality with environment variable support.

Here's the usage: `keep {secret, order} {get, create, delete, list}`

You can add keep to your path by running 'python setup.py develop'.

To setup environment variables, refer to bullet 4 of this link: http://docs.openstack.org/grizzly/basic-install/apt/content/basic-install_controller.html#basic-install_controller-keystone

One thing we might want to discuss is the `__str__` method of orders and secrets that I modified. Maybe some attributes should be excluded, such as algorithm, cypher type, etc.