Please make the wiki/API URL configurable

[mgorny]

Hi,

This looks like a really cool tool and I'd like to use it with our MediaWiki instance. However, it seems that the code hardcodes URIs specific to Wikipedia and sister projects, and even with hackery I won't be able to make it use our wiki (mostly because of harcoded /w/ path, I guess). Could you please make all paths configurable, so that the tool could be used with any MediaWiki instance? TIA.