Update project to Ruby 2.7.2
In the spirit of: &2380 (comment 425890939), updated the project to use Ruby 2.7.2.
Because of a chicken and egg problem, installed Bundler 1.17.3 for compatibility. With both versions of Bundler present, it should be possible to use auto-switch: https://bundler.io/guides/bundler_2_upgrade.html#version-autoswitch.
With this merged, the updated Docker image file should work when deployed.
Edited by Evan Read