version to 1.9.0
version to 1.9.0

* mass-switch strings from `'` to `"` 7c4bae8
* update to our more modern conventions #36
* setup CircleCI test runs b8ab414
* switch to including Gemfile.lock in the repo a051fa2
* formally drop support for ruby 1.8.7; tweak CircleCI config 2035306
* run CircleCI against rubies 2.3.7, 2.4.5, 2.5.3 f27266a
* add `.gitkeep` files for test/system and test/unit dirs #37
* update to generate CircleCI config for multi Ruby version checks #38

redding/ggem,redding/ggem