Added recursive_query function, fixes #6

[zeedo]

Queries for SOA and NS now recursively search each domain and non-existing domains display an error instead of a stack trace.

Made wildcard handling a bit nicer:
When we find a wildcard user might be interested in seeing the IP. If wildcards exist the brute forcing code should ignore any subdomains that match the wildcard IP, otherwise all subdomains return an IP and the output has too much false positive noise.

[mschwager]

I think we could make this a bit more Pythonic, and use the builtin features of dnspython with something like the following:

tld_length = 2
for _ in range(len(domain) - tld_length):
    resp = query(resolver, domain, record_type)
    if resp:
        break
    domain = domain.parent()
else:
    return None

return resp

[johanmazel]

The db4d0bc introduces an error (sorry I am not exactly sure how to refer a commit on another repository).
If the wildcard fails, its type is None
Consequently, this generates an error when each a A query is made on each subdomain because fierce tests if the A query result is None or if the found address is the same as the wildcard (which is None here).
There should an additional test for wildcard.