Add option to ignore vulnerabilities by the id

[rtfpessoa]

Add --ignore option to allow passing a comma separated list of ids to be ignored in the analysis.

[harman28]

What kind of IDs would these be? Package names in some form?
Could you give an example of the desired usage?

[rtfpessoa]

In the output if you request -f json you should receive an id field for each vulnerability. e.g.: nodesecurity:npm:brace-expansion:2017-04-25