Add ability to modify SVG props, style and SVGO config

This release adds the following options:

1. The ability to pass custom SVG props (such as namespaces, aria attributes, etc) to the SVG sprite using the -p or --props flag. Use -p "" to remove any attributes.
2. The ability to pass custom inline style to the SVG sprite using the -s or --style flag. Use -s "" to remove any inline style.
3. The ability to disable optimization of input files using SVGO. Just pass -c false or --config false to do this.