Kenya: Improve Mzalendo scraper

[tmtmtmtm]

• [x] Once https://github.com/mysociety/pombola/issues/2130 is done, pick this up as identifier__mzalendo
• [x] Get people who have ended their memberships during the current term
• [x] Pick up start and end dates of Memberships (e.g. for http://info.mzalendo.com/person/judah-ole-metito/ and http://info.mzalendo.com/person/alfred-bwire/experience/)
• [x] Pick up the nominated members / women's representatives
• [x] Pick up both names for people: e.g. http://info.mzalendo.com/person/rose-auma-ogendo/
• [x] Resolve any other duplicate memberships shown from the Membership Matrix (e.g. Shakila Abdalla vs Shakila Abdalla Mohamed)
• [ ] Add historic terms
• [ ] Similar scraper for the Senate

[chrismytton]

identifier__mzalendo column added in https://github.com/tmtmtmtm/kenya-mzalendo/commit/663f1606c4e520d04133ebae005b5d5c732f6296.

[mhl]

You can now find historic terms (well, currently the one historic term) via: http://info.mzalendo.com/sessions (that unadvertised URL is likely to be renamed with mysociety/pombola#2179).

Note that the people shown on each page are picked because they have a position which matches the ParliamentarySession house / position_title and the position's start_date / end_date overlap with that session's start_date / end_date. However, many of the position start_date / end_date values are approximate dates, so a position from 2003 to 2007 (approximate dates) is almost certainly meant to mean just someone in the 9th Parliament of Kenya (2003 -> 2007) term of parliament, but the code currently will assume this overlaps with the 10th Parliament of Kenya (2007 -> 2013) because its start date is 2007-12-28 .

So there may be some false positives for the moment - the scraper will need to check the person's page and look at the dates. Or there are a couple of ways to deal with that on the Pombola end.

Related to: mysociety/pombola#2171 (PR: https://github.com/mysociety/pombola/pull/2172 )