Making signal handling ruby 2 compatible

by stealing the pattern used in Sidekiq :scream_cat:.
Merge pull request #344 from meatballhat/ruby-2-compatible-signal-handling

Making signal handling ruby 2 compatible
Prepping for v2.5.1 release
Merge pull request #345 from meatballhat/v2.5.1-prep

Prepping for v2.5.1 release
Slightly better handling of string and array forms of `every`

Fixes #338
Making dependency versions more specific for 2.5 stable

although I fully admit that I don't understand how the `~>` operator
works.
Merge pull request #349 from meatballhat/tightening-up-dependencies-for-2.5-stable

Making dependency versions more specific for 2.5 stable
Prepping for v2.5.2
Merge pull request #350 from meatballhat/v2.5.2-prep

Prepping for v2.5.2
Merge pull request #348 from meatballhat/better-handling-of-string-and-array-every

Slightly better handling of string and array forms of `every`