0.4.0

Added

• Line charts.
• Box plots.
• Bar charts.
• Introduce categorical representation, views and axes.
• Add ability to set dimensions of plot (PR #8)
• Added ability to display a histogram as densities
• Add ability to display grids (PR #23)

Changed

• Change create_axes, save, to_svg and to_text to return Result indicating an error.
• Make representation module public.
• Rename Scatter::from_vec to Scatter::from_slice.
• Rename Histogram::from_vec to Histogram::from_slice.
• Rename view::View to view::ContinuousView and introduce view::View as a trait.
• Change svg_render functions to take data slices rather than Representations.
• Histogram::from_slice now takes either a bin count or a bin bound list as its second argument.