upgrade chartkick dependency v3.3.0

[patriciojofre]

No description provided.

[masonhensley]

@patriciojofre - CI is failing with this message

You are trying to install in deployment mode after changing
your Gemfile. Run `bundle install` elsewhere and add the
updated gemfiles/rails_6.gemfile.lock to version control.

[michelson]

we should document this, but to get the green build from travis this command is necessary bundle exec appraisal install and then commit the locks, running a bundle install will be a good idea too.
this is true for #45 too

best