fix: Require active_support before use

[olleolleolle]

This PR attempts to fix a thing seen in the test output here: https://github.com/roidrage/lograge/runs/4777416627?check_suite_focus=true

This has changed in later releases of ActiveSupport, see this Issue: rails/rails#43851

[olleolleolle]

@iloveitaly This repairs a bunch of issues, and makes the test suite sort of run.

Now, there are failures like:

activesupport-7.1.0.alpha requires ruby version >= 2.7.0, which is incompatible
with the current version, ruby 2.6.8p0 (jruby 9.3.2.0)

Update: Skipped JRuby for Rails 7 in #341

[iloveitaly]

Awesome! Great changes. Keep them coming :)