Refactor trusttrees.py, add pre-commit hooks

[KevinHock]

This should have the exact same functionality as before, I mainly tried to DRY up the code a little while I read it. The git history should make things more clear than the big diff.

~I am going to release the code as it is now on PyPI, before we merge this in.~ (Done.)

Some of the changes are:

• Add pre-commit, run hooks
• Add metavar for domain check argument
• Use default value for --export-formats
• Add ipdb to requirements-dev.txt
• Use dns.rdatatype.NS instead of 2
• Make constants for colors
• Delete dead functions
• More pythonic not foo in bar -> foo not in bar refactors
• Change max_depth to constant, so it is more DRY
• And refactor loop to list comprehension
• Fix spelling of authoritative w/r/t is_authoritative
• Refactor most string formatting to use .format()
• DRY calling get_graph_data_for_ns_results()
• Make all TODOs the same format
• Add some keyword args where it would add clarity
• dns_query_error_occured (bool|str) -> dns_query_error (None|str)
• DRY and dedent hadouken code in _ns_query()
• Fix spelling of authoritative in comments
• DRY and dedent code in _enumerate_nameservers()
• Change constant name from DEFAULT_RESOLVER to DNS_WATCH_RESOLVER
• Standardize imports
• Organize global variables a little

[KevinHock]

Made #13 instead of this, due to a rebase issue.