Pyelastictest

----------------

- Use `wait_for_*` arguments to `health` call to simplify waiting logic.

----------------

- Filter out all log messages during `cluster.wait_until_ready`.

- Issue 5: Redirect subprocess stdout/err to files and log those as debug
logging messages when a node is stopped.

- Expand documentation.

----------------

- Allow configuration of ip instead of hardcoding `127.0.0.1`.

- Add `isolated.isolated` context manager.

- Add basic API documentation for all public modules.

- Allow explicit configuration of all cluster ports.

- Add an `urls` property to the cluster, to expose a list of client urls for
all cluster nodes.

----------------

- Initial version based on code from Mozilla monolith and on ideas and code
from kazoo.