Core-SNP-filter v0.2.0

Some enhancements in this release based on feedback from @tseemann:

• Improved error messages
• Better formatting of stats displayed to stderr
• Replaced --verbose option with --table
• Added --invariant_counts option to help with IQ-TREE

The main functionality of the tool is unchanged from the previous version.

Tarballs of pre-built executable binaries are attached:

• coresnpfilter-linux-x86_64-musl-v0.2.0.tar.gz: for Linux systems with x86-64 processors
• coresnpfilter-macos-aarch64-v0.2.0.tar.gz: for Macs with Apple silicon processors
• coresnpfilter-macos-x86_64-v0.2.0.tar.gz: for Macs with x86-64 Intel processors

If none of the above work for you, you'll need to build Core-SNP-filter from source (see the README).