- Create tickmode "proportional"
- Map fractional tickvals to axis values w/ axis range:
  - Set ax.(minor?).tickvals to
  - Do that right before `arrayTicks()` is called
- Every instance of `tickmode === "array"` gets `...|| "proportional"`

This works well since tickmode "proportional" really just adds a preprocess step to
tickmode "array".

TODO:

- Check if graph is reversed
- Find where ticks are redrawn on zoom and make redraw proportional (will probably fix below)
- Figure out why ticks not redrawn on double click/home
- Add docs in layout

The algo has to set the tickvals property back to original value after
spoofing it. This does that.

Plotly does some math on the ticks, sometimes comrparing major and minor
values, so we have to store both in their own separate values and then
restore them to their attribute at the very end so plotly has them
throughout the calculating process.

These tests currently fail but this commit currently doesn't include
fundamental bug fixes.

So, parameterization is good in testing.

Promises + Jasmine + Karma w/o let or const make it hard to do manually.

There should be a parameterization library.

There is a way to make it all work (moving all loops outside of
it/describe).

Which is good, because then each parameter can be reported as a separate test,
which improves reporting. But that solution is generally unpopular.

…icks

- Use private ax._mappedTickvals instead
- Remove use of Lib.nestedProperty during refactor