Added host_to_mask method and added tests for it
Use host_to_mask so we can negate a mask. Also added documentation.

A custom provider should probably be aware that these kind of masks are possible.
Add test to see if type takes negative values
Added fixtures to test parsing negated addresses
Fix parsing negated values
Fix parsing of rules and generating the command line to set the rule
spec test fixtures should represent real use cases
Generic generating command line options for negated rules
Added a test case for /older/ alternative negation syntax
Use a more generic way for parsing negated options, not only for destination and source
fix negation handling for complex arguments
update spec for host_to_mask to override Resolv
Merge pull request #267 from phemmer/negation_support

Negation support