Removing old classes

Signed-off-by: Jonathan Almeida <jonathan@snowplowanalytics.com>
New Tracker class

- trackPageView added

Signed-off-by: Jonathan Almeida <jonathan@snowplowanalytics.com>
Adds context via completePayload
Added setSchema

- The right way. Should be done similarly in snowplow/snowplow-ios-tracker#47