More control to multiple Y-Axes (Chartjs 2.0)

[anttimann]

#365 More control to multiple Y-Axes

Changed chartYAxes to an array that matches to datasets by index.

Here first and third dataset would go to Y-Axis 1 and second to Y-Axis 2
chart-data = [[1,2,3], [4,5,6], [7,8,9]]
chart-y-axes = ['y-axis-1', 'y-axis-2', 'y-axis-1']

Pull Request check-list

• Run gulp test to ensure there are no linting, or style issues and all tests pass.
  [Some font differences in labels of .png files]
• Squash your commits into a few commits only.
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• Have you updated the documentation and / or examples?
• Have you included a new test?

[jtblin]

Thanks @anttimann 👍
Published 1.0.0-alpha5.