Debug print statements should be --verbose only

All the print statements in Plugin.py make this module unwieldy in Nagios.  It prints out the following debug information before the status is printed out:

checking warning
range was warning
(0, 20.0, False)
0.0:0:20.0 =  False
checking critical
range was critical
(0, 50.0, False)
0.0:0:50.0 =  False

Since this is all printed out first then all Nagios ever displays as a status is it's service summary is "checking warning".  These statements should all be printed only if self.options.verbose is set.