Change deprecated types for OTP 17

Addresses these warnings under OTP 17:

src/meta.erl:96: type dict/0 is deprecated and will be removed in OTP 18.0; use use dict:dict/0 or preferably dict:dict/2
src/meta.erl:102: type dict/0 is deprecated and will be removed in OTP 18.0; use use dict:dict/0 or preferably dict:dict/2
src/meta.erl:268: type gb_set/0 is deprecated and will be removed in OTP 18.0; use use gb_sets:set/0 or preferably gb_sets:set/1
src/meta.erl:269: type dict/0 is deprecated and will be removed in OTP 18.0; use use dict:dict/0 or preferably dict:dict/2