Add appsflyer pod dependency
appsflyer: add setup
appsflyer: add -start
appsflyer: add -identify
appsflyer: add -applicationDidBecomeActive
appsflyer: add -track
appsflyer: fix -track
appsflyer: fix test
appsflyer: fix tests
appsflyer: fix types
appsflyer: add currency
Merge pull request #185 from segmentio/add/appsflyer

add support for appsflyer