Remove include file and add type tinymt32:intstate32/0

* Move the content of include/tinymt32.hrl into src/tinymt32.erl

* Define new opaque type for tinymt32:#intstate32{} as tinymt32:intstate32/0

* Change all type spec in src/tinymt32.erl to use intstate32() instead of #intstate32{}

* Change src/tinymt32_tests.erl to use tinymt32:intstate32/0 type

* Change src/tinymt32_tests.erl type spec to use non_neg_integer()
  instead of tinymt32.erl local type uint32()