Add capacity for axis position

[JulianKingman]

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Closes #189

[marzolfb]

My apologies for taking so long to respond to this PR. I took this PR for a test drive and added the position option to the axis options for the "StockLine - Basic" chart on the example app (just like you added to the docs) and I came up with something like this:

Did you intend for the text labels to go "inside" of the axis lines (i.e. to the bottom of the axis line at the top and to the left the axis line at the right)?

[JulianKingman]

@marzolfb the orient property for the labels addresses that, doesn't it?

[marzolfb]

You're right - I should've started with that screenshot instead. If you change the same example above to orient to 'top' on the x-axis and 'right' on the y-axis, you get this odd output:

I assume you must be working with a dataset+options in your testing that doesn't show the same odd behavior?