add new hier_config option ('no' commands exception)

[rbartzen]

Add a new option to replace the command line expression for specifics ios exceptions (regex) - negation case.
e.g. no ip access-list A seq B

[jtdub]

Hi @rbartzen -- Can you write a test case for this?
@jdrew82 -- does this fix #101 ?

[jdrew82]

This does look like it'd address that, though I think it'd be better if it applied to all lines, not just negations.