Added support for saving individual Pokemon IVs
Added support for saving individual Pokemon IVs

* Modified Pokemon.get_active to include IVs in returned array (if available)
* Added Pokemon.seen_before to return true iff the specified encounter_id has been seen before

* Added model PokemonIVs

* Modified parse_map to only add a pokemon to the pokemons array if it hasn't been seen before
* Modified parse_map to return the newly found pokemon array

* Modified create_tables, drop_tables and database_migrate to handle new PokemonIVs model

tsuncp/PokemonGo-Map,tsuncp/PokemonGo-Map,tsuncp/PokemonGo-Map,tsuncp/PokemonGo-Map