Svgis

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* Remove periods and number signs from classes and ids.
* Refactor classing functions to svgis.style
* Improve error messages when drawing features.

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* Make inlined styles default
* Handle empty files without complaining
* ignore topological errors when clipping

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* Add precision argument for `svgis draw`

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* Add `svgis graticule` command line tool
* Ensure no repeated style rules when inlining CSS.
* Round numbers at the last minute in the svg module. This is quicker.
* Improve py 2/3 compatibility, esp. when testing.

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* Fix problem reprojecting bounds with mixed projections.
* Add cli tool for getting bounds of a layer
* Repair --verbose option.
* Add `svgis bounds` command line tool for checking the bounds of a layer.
* Expand tests (coverage now above 90%)

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* change `--project` option to `--crs`.
* Fix error with empty CSS selectors
* Add quiet and verbose logging options to `svgis draw`.
* Fix simplification in `svgis draw`.
* Ensure that geojson layers get a pretty name.
* Regularize `svgis.svg`, adding tools for creating more SVG elements, even those not directly used here.
* Try, just slightly, not to have infinite bounds
* Expand docs.