Restructure large parts of the Extension, add the [table-chart] Shortcode in a different and more robust way.
Update documentation and readme files after changes in 0.6, where we switch to a `[table-chart]` Shortcode, see https://github.com/soderlind/tablepress_chartist/issues/2.
Merge pull request #4 from TobiasBg/master

Refactor the implementation of the [table-chart] Shortcode