Bump version to v5.0.0

Merge pull request python-telegram-bot#348 from python-telegram-bot/u…

…rllib3_fix_proxy_auth

Urllib3 fix proxy auth

Bump version to v4.3.3

Bump version to v4.3.2

Bump version to v4.3.1

Bump version to v4.3

Bump version to v4.2.1

bump version to v4.2.0

bump version to 4.1.2

bump to 4.1.1