flackou

Fix Rails 5.2 incompatibility

1

Following [my comment](https://github.com/mwlang/rails_wordpress/pull/3#issuecomment-382455857) on PR #3, I propose this change to fix the error raised on app loading with Rails 5.2 : ``` NoMethodError: undefined method `sqlite3=' for ActiveRecord::Base:Class .../rails_wordpress/lib/rails_wordpress/railtie.rb:9...