* fix warnings
* do not get json_lib from environments
* do not use global timeout from environments (adjust behaviour to other database adapters), so
  it should be seted explicitly per call if needed
* change getting adapter via `transport` option

* refactor HTTP adapter
* use process-less Mint adapter to not copy data between caller and socket
* remove uncontrolled producing of atoms from http (random atom names for a pool)
* remove multiple encode/decode from http (so if something needs to be transformed, will be only once)