Easychart

New features
- `chart.vline` and `chart.vband` now allow for an optional `xAxis` argument to handle charts with mutliples axes
- `chart.hline` and `chart.hband` now allow for an optional `yAxis` argument to handle charts with mutliples axes
- saving the `easychart.config` will now write the config file with indentation

Bug fixes
- `easychart.Chart.save` now ignores NaN values when serializing to a json file
- the `colormap` argument was ignored in `easychart.heatmap`; now fixed
- `easychart.heatmap` will now set yAxis and xAxis bounds (`min` and `max`) to ensure sparse matrices are rendered

Docs
- Added and updated docs

New features
- add `colormap` argument in `easychart.new`
- dynamically dispatch arguments to `easychart.new` from `easychart.heatmap`

New features
- copy chart as PNG option in exporting menu
- argument aliases in `chart.vband` and `chart.hband` for `min`, `max` and `color`
- text labels for `chart.vband` and `chart.hband`
- convert integer `color` to `colorIndex`

Deprecations
- `chart.append` is now deprecated

Bug fixes
- `easychart.plot` passes arguments to `easychart.new` based on function signature