CQS - Answer distribution charts scaling

Also did some refactoring and added a number of comments in the chart
generator to ease future maintenance.

Removed "grunt-notify" module because it's too annoying and hardly
useful.

Closes CNVS-16518

TEST PLAN
---- ----

  - create a quiz with two FIMB questions
    + the first question should have over 10 possible answers (could be
      right or wrong, doesn't matter)
    + the other question could have like 3-4, like normal ones
  - take the quiz by quizard or manually; we'd like to have a number of
    responses to give the chart some shape
  - turn on new stats FFlag
  - go to stats page
    + verify the chart scales for the first question as described by the
      ticket and its AC
    + verify that the chart for the second question looks almost like
      the one on master/the normal one .. e.g, the bars are 30 pixels
      wide
    + make sure you can trigger the tooltips for every bar out there

Change-Id: Ifb1ee3e2359f0c3d77d733bba6262a46df8ced0b
Reviewed-on: https://gerrit.instructure.com/43404
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Ahmad Amireh <ahmad@instructure.com>