Handling MediaWiki revisions which pandoc cannot parse

[peterjc]

I've seen this with mal-formed tables (where the user generally fixed the page in a subsequent revision).

Currently these problem revisions are simply ignored (which is fine if the user fixed the issue themselves in the next revision, we end up with a combined commit)

[peterjc]

In v2.0.0 of the script (i.e. the current master), the process is now:

• Convert XML dump into mediawiki files, commit those to git
• Human may choose to remove spam commits and reverts/cleanups
• Convert mediawiki to mardown ready for GitHub pages

i.e. This avoids problems with trying to commit converted versions of broken revisions.