Improved `dnsping` tool

What's Changed

• Add -m flag to enforce cache-miss
• Add -r flag to clear RD flag (disable recursion)
• Bump dependency versions to latest
• Remove support for python 3.4 - 3.6
• Other minor quality of life improvements

New Contributors

• @cpswan made their first contribution in #90
• @oBusk made their first contribution in #91
• @leleobhz made their first contribution in #94
• @xhdix made their first contribution in #93

Full Changelog: v2.0.2...v2.1.0