import population data from geonames

[missinglink]

copied from #212

some geonames imports/concordances are missing the associated population metadata.

eg:

• https://whosonfirst.mapzen.com/spelunker/id/101750367/
• http://www.geonames.org/2643743/london.html

for the record above I'd expect the WOF record to have a population value of 7556900

I'm not sure about the scale of the problem, I found this when running our acceptance test suite and found that it affects searches for: brooklyn, london, portland, paris etc.

we are using the population data in pelias to score more populous places higher in the results (eg London UK vs. London ON) so it's important that we can get this fixed ASAP.

thanks!

[missinglink]

maybe this has been fixed? checking pelias code first

[missinglink]

yes, apologies its an import error as per pelias/whosonfirst#106