remove use of Ember.Logger

[Melanie Sumner]

We need to remove the use of Ember.Logger:

https://emberjs.github.io/rfcs/0297-deprecate-ember-logger.html
https://deprecations.emberjs.com/v3.x#toc_ember-console-deprecate-logger
Using Ember.Logger will emit warnings/deprecations since Ember 3.2.

[Andrew A Lee]

Will publish a new release of the addon after addressing #124.