README file update

add --accept-license to AppVeyor

PEP8 fixes

updated documentation

code modernization, added deploy script

Transition to Python 3.6-3.8.

version bumb

Merge branch 'fix-keywords' into 'master'

keywords metadata are optional

[fix] Python2 import fix

[add] pre-config hooks

[add] pre-commit hooks

[style] code modernization

[fix] download link is replaced with canonical URL.

[add] some minimal metainformation about the record