Catch YAML data merging errors as user errors.
In CLI update Kitchen.logger level when passed in via argument.
Add a more helpful error message when a driver could not be loaded.

References #80
Reformat exceptions and errors with friendly messages in serial mode.

Currently this only handles non-parallel mode.
Roll instance crash message into one line.
Log celluloid activity to its own log file.
Merge pull request #81 from opscode/error-reporting

Error report formatting