Julia

- Add GR dependency to make it the default backend
- Improve histogram2d bin estimation
- Allow vector arguments for certain series attributes and support line_z and fill_z on GR, PyPlot, Plotly(JS) and PGFPlots
- Automatic scientific notation for tick labels
- Allow to set the theme in PLOTS_DEFAULTS
- Implement plots_heatmap seriestype providing a Plots recipe for heatmaps

- fix 3D plotting in PyPlot
- Infinite objects

- fix scientific notation for labels in GR
- fix labels with logscale
- fix image cropping with GR
- fix grouping of annotations
- fix annotations in Plotly
- allow saving notebook with plots as pdf from IJulia
- fix fillrange and ribbon for step recipes
- implement native ticks that respond to zoom
- fix bar plot with one bar
- contour labels and colorbar fixes
- interactive linked axis for PyPlot
- add `NamedTuple` syntax to group with named legend
- use bar recipe in Plotly
- implement categorical ticks

- improve resolution of png output of GR with savefig()
- add check for ticks=nothing
- allow transparency in heatmaps
- fix line_z for GR
- fix legendcolor for pyplot
- fix pyplot ignoring alpha values of images
- don't let `abline!` change subplot limits
- update showtheme recipe

- fix plotly bar lines bug
- allow passing multiple series to `ribbon`
- add a new example for `line_z`

- Add linestyle argument to the legend
- Plotly: bar_width and stroke_width support for bar plots
- abline! does not change axis limits
- Fix default log scale ticks in GR backend
- Use the :fontsize keys so the scalefontsizes command works
- Prepare support for new PlotTheme type in PlotThemes