Plots.jl: New series types

[tbreloff]

I'll try to consolidate a list of to-be-implemented series types/recipes here. Please comment if you want something added to the list (and include an example usage/picture!). In general, many of these visualizations can be implemented as recipes which are composed of several lower-level components (polygons, lines, etc). This way all backends can support all the plots.

• [x] [Error bars](https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/errorbars.ipynb)
• [x] [Box plots](https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/boxplot.ipynb)
• [x] [Violin](https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/boxplot.ipynb)
• [x] [Quiver](https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/quiver.ipynb)
• [ ] 3D Quiver
• [x] [Polar plots](https://github.com/tbreloff/Plots.jl/issues/181)
• [ ] Graphs (connected nodes)
• [ ] Aster (http://johnmyleswhite.github.io/Vega.jl/asterplot.html)
• [ ] Horizon (http://johnmyleswhite.github.io/Vega.jl/horizon.html)
• [ ] Population (http://johnmyleswhite.github.io/Vega.jl/popchart.html)
• [x] [Ribbon](https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/errorbars.ipynb)
• [ ] [Choropleths](https://github.com/penntaylor/ChoroplethMaps.jl)
• [ ] [grouped histograms](https://github.com/tbreloff/Plots.jl/issues/254#issuecomment-218760020)

For anyone looking to contribute, this is a easy way to get involved as these are pretty self-contained projects.

[tbreloff]

I kicked off a new internal framework with box plots. Here's an example usage: https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/boxplot.ipynb

The gist is that I have a hook to be able to swap out series arguments after most of the processing has happened, but before it's passed to the backend code. The dispatch happens based on the value of the linetype symbol.

This lets me build a given series from component series. See the boxplot implementation as an example.

For anyone wanting to implement new plot types... this is the way to do it.

[tbreloff]

Violin plots done... I added an example to https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/boxplot.ipynb

[tbreloff]

Error bars: https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/errorbars.ipynb

[tbreloff]

Quivers: It's not perfect, but it's mostly working. See https://github.com/tbreloff/ExamplePlots.jl/blob/master/notebooks/quiver.ipynb

The notebook mirrors the matlab example: http://www.mathworks.com/help/matlab/ref/quiver.html

[tbreloff]

contour3d: It seemed easy to add, so I did:

[tbreloff]

Added contours keyword for surface and wireframe plots:

[tbreloff]

Closing in favor of "Recipe ideas" issue