issue #9 and issue #10 resolved, minor updates to README.md

- catching NoSuchElementException when db.runCommand() is called without arguments and translating that into a CommandResult setup to mimic what the official shell would return
- Mongo constructor sets JavaScript 'host' variable at the end using the specified hosts so the JavaScript toString() call will return the correct result
- test coverage for both issues added
- version of mongodb tested against indicated at top of README.md
- minor formatting changes
- pledgie icon added to README.md