Bump the minimum required version of `requests`.
Bump the minimum required version of `requests`.

This version of `requests` depends on `urllib3>=1.21.1`.

To properly silence various deprecation warnings with those old
library versions we explicitly depend on `urllib3>=1.26.0`.
The `1.26.x` version range also happens to be the last one to support
our lowest Python 3 target, Python 3.5.

jjjake/internetarchive