remove Debian python-protobuf dependency

[hongxuchen]

Short Description:

Debian python-protobuf dependency removed (install.sh/setup.sh);
docs/installation.md not synced

Fixes (provide links to github issues if you can):

• during installation of pgoapi, protobuf will automatically be a
  dependency (confirmed with pip show pgoapi)
• Even for Ubuntu 16.04 LTS, python-protobuf version is
  2.6.1-1.3, which is too old
  • confirmed with apt-cache show python-protobuf
  • see issue pgoapi.exceptions.PleaseInstallProtobufVersion3 #1815
    (pgoapi.exceptions.PleaseInstallProtobufVersion3 #1815)

[mention-bot]

@hongxuchen, thanks for your PR! By analyzing the annotation information on this pull request, we identified @joergpatz, @simonsmh and @acaranta to be potential reviewers

[hongxuchen]

The problem for the issue before was that after python-protobuf (through apt-get/apt/aptitude) was installed before, there is no way to uninstall it via sudo pip uninstall.

However problem still exists when python-protobuf was installed beforehand. Therefore the exact solution should be checking whether such a dependency is present (apt-cache policy python-protobuf and pip show protobuf) and issue a warning when the version is below 3.

[solderzzc]

Please PR to dev branch. Thanks.

[hongxuchen]

Created a new one #3610 , thanks.