Ziaplot

- Updated Pie and Bar interfaces
- Fixed legend text spacing
- Added context manager for axes and layouts
- Allow more than 2 colors in colorfade
- Added contour plots
- Added LayoutGap for leaving space in a Layout

- Implement ziamath's Text object for plot labels
- Added size property to plot style, combining canvas width and canvas height
- Added global configuration object

- Added an option to use SVG1.x format for compatibility since SVG2.0 is not fully supported in all browsers/renderers yet.

- Use ziamath library to draw math text.

Initial Release