Added a helper methods for manually running service handlers

This adds a few helper methods for manually running a service
handlers. These helper methods make running service handlers
easy to run given a handler class and some params.
Added a global `logger` configuration for Sanford

This adds a global `logger` configuration for Sanford that is now
used as a default for host's configuration, `Runner` and
`TestRunner`. It defaults to a null logger, but can be set
globally. This is particularly useful when manually running
service handlers, so they use the default configured logger.
Merge pull request #62 from redding/jcr-nicer-runner

Added a helper method for building a `Runner` with only params