Add test for get_categories_from_text
Add test for get_categories_from_text

This method parses wikitext looking for categories using regexes.
Add simple test checking no results, one result and two results.

danmichaelo/wm_metrics,Commonists/wm_metrics,danmichaelo/wm_metrics,Commonists/wm_metrics,danmichaelo/wm_metrics,danmichaelo/wm_metrics,Commonists/wm_metrics,Commonists/wm_metrics