Retry deprecation warning

[simeonreusch]

I get a deprecation warning from Retry:

DeprecationWarning: Using 'method_whitelist' with Retry is deprecated and will be removed in v2.0. Use 'allowed_methods' instead

Should be super easy to fix :-)

[mcoughlin]

@simeonreusch In that case, want to open a PR?

[simeonreusch]

Could you push this to pypi? That would be great :-)

[mcoughlin]

@dmitryduev Do you want to give me pypi permissions for this? Or do it yourself?

[dmitryduev]

@mcoughlin invited you to pypi :)