LibSecRm 3.2 released!

Significant portability updates. LibSecRm now compiles on FreeBSD and macOS (as provided by Travis CI): https://app.travis-ci.com/github/bogdro/libsecrm.
Allow setting the number of iterations using an environment variable.
Improvements in banning.
Improvements in the build system.
Improvements in code quality.
Significant improvements in the documentation.
New unit tests.