Added exception handler to core.py for when IPv6 packets are processe…

…d that do not have fragmentation flags set in their headers.

Update README

Updated README file with new requirements, information, and example output

Major version update/rewrite to Dshell, now using Python 3. See READM…

…E for more details.

Highlights:
- This is a major framework update to Dshell. Plugins written for the previous version are not compatible with this version, and vice versa.
- Uses Python 3
  - Rewritten in Python 3 from the ground up. Python 2 language deprecated on 1 JAN 2020
  - By extension, dpkt and pypcap have been replaced with Python 3-friendly pypacker and pcapy (respectively).
- Is a Python package
- All plugins are chainable
- Plugins can use all output modules
- Improved error handling
- Enables development of external plugin packs, allowing the sharing and installation of new, externally-developed plugins without overlapping the core Dshell libraries.

Update README.md

Dshell 3 announcement