Small bug fixes and improvements

Improved JSON output and bugfixes

Add support for DoT, DoH and DNSSEC

* Add support for DNSSEC
* Add -F to display flags for each response (dnsping)
* Display full response in verbose mode (dnsping)
* Add DoT (DNS over TLS) support (dnsping, dnseval)
* Add DoH (DNS over HTTPS) support (dnsping, dnseval)
* Add TCP support
* Refactor and PEP8 cleanup
* Do not use system resolver when not needed
* Add support for user defined source IP address
* Add user-specified destination port (-p/--port)
* Improve error handling
* Display last response code for each entry
* Rework custom socket and custom TTL support
* Rework time calculation logic to eliminate an extra DNS request that was just sent for timing (dnstraceroute)
* Update docs (output samples, use cases, etc)
* Use proper terminology (in code) to reduce confusion

JSON Export and Bug Fixes

- Add JSON export [commit dd1f453]
- Ignore unrelated ICMP messages [farrokhi#62]
- Fix statistics calculation [farrokhi#64]
- `-c 0` for infinite ping [farrokhi#57]
- Flush output messages [farrokhi#59]
- Update sample public resolver data

Preparing for v1.6.4

General improvements and fixes

Update installation notes to reflect recent changes

No more needed

Add color mode to dnseval ("-C" option)

Bump version

Remove dnspython from external requirements