gpg encryption support (#162)

* gpg encryption support

* gpg encryption support

* refinement

* refactor using protonmail opengpg

* warning

* remove exception in linting

* reduce I/O on decrypt

* fix typo

* streaming in encrypt

* Update README.md

do not reference server public hosting version in encrypt/decrypt headers example

* linting

* linting fix

* increase default random-token-length to 10