Remove deprecation warning for hit constructor.
Update dependencies to target redis-rb 3.0 and Redis 2.6.

All reporting commands now return floats where appropriate, this
includes:

Tracker#hit_count
Tracker#hit_count_for_session_id
Tracker#top

This does not include Tracker#uhit_count since it uses ZCARD under the
hood.
Documentation fixes.
Moved uhit_count functionality into hit_count.
Started work on 1.0 release notes.