v2.1 release

Core

• change default hash function to xxHash's XXH3 for insane performance gain
• --line-max-size now defaults to 64 instead of 14, to avoid bad UX (closes #10)
• improve debug display, with human representation of sizes via sizerepr()
• add #pragma to ignore specific unwanted gcc warnings (b6ecc8b)
• remove deprecated content on code base (c96fdce, d79712d)

Integration

• add support for Mac OS X from Xcode 8.3 to 12u (closes #9)
• test every wordlist with multiple --line-max-size values
• test every wordlist with & without --printable option
• add new test wordlist: words_len1-300_withdups_shuffle.txt
• upgrade travis-ci built matrix with Linux & OS X builds for x86 & x64
• add debug output for memstate variables (3d1d4a0)