Compare app converts multiple parameters of the same type to arrays

[orangejulius]

Complicating our analysis of pelias/api#744, the compare tool actually changes the requests it sends along to Pelias.

For example, a query (http://pelias.github.io/compare/#/v1/reverse%3Flayers=region&point.lat=47.417&point.lon=10.75&size=3&sources=geonames&sources=gn) that contains two sources entries actually ends up being sent to pelias with square brackets (in this case, as http://pelias.prodbuild.mapzen.com/v1/reverse?layers=region&point.lat=47.417&point.lon=10.75&size=3&sources=["geonames","gn"] )