Fixed RequestCallback has to import Foundation before defining protocol (fixes #202)
Fixed RequestCallback has to import Foundation before defining protocol (fixes #202)

iamjason/snowplow-objc-tracker,redengineer/snowplow-objc-tracker,chunkyguy/snowplow-objc-tracker,redengineer/snowplow-objc-tracker,chunkyguy/snowplow-objc-tracker,snowplow/snowplow-objc-tracker,snowplow/snowplow-objc-tracker,snowplow/snowplow-objc-tracker,snowplow/snowplow-objc-tracker,iamjason/snowplow-objc-tracker,iamjason/snowplow-objc-tracker