add security audit documentation

use /etc/ssl/cert.pem to validate HTTPS trackers and web servers on M…

…acOS

Merge branch 'RC_1_2' into RC_2_0

update revision

fix contributing docs

bump version to 1.2.11

fix issue where pad blocks would skip the zero-hash check and conside…

…r the last piece as passed, which in turn could cuase a hybrid magnet link to fail with inconsistent-hashes

fix issue where pad blocks would skip the zero-hash check and conside…

…r the last piece as passed, which in turn could cuase a hybrid magnet link to fail with inconsistent-hashes

bump version to 1.2.10

bump version to 1.2.10