Fixes #2
Now debug messages are shown only in the correct log level. The
debug messages came from Celluloid. Its logger is now Chef::Logger

Chef::Logger is now used instead of the custom KnifeESX::CLogger
(I ignore the reason of its existence, hope this commit doesn't break
 anything)
Removes Celluloid as dependency
Merge pull request #7 from tommyblue/master

Fixes #2