added replacement of aiohttp Connector via kwargs

Added a way of providing a custom connecter, Actual intend is being able to provide a connector with custom init settings.

There was already the unused kwargs argument. So I just used this, as I figured that the use for it is niche enough that it does not warant its own argument.

My Reason: I deal with an nextcloud server with some heavy rate limit and it is almost imposible to use the library, with the default aiohttp Client connection settings.

I hope this is welcome even if nichè.

Also my formatter seems to removed trailing whitespace and converted tabs to spaces in the comments. I am to github inept to fix this. Is the removal of trailing whitespace a problem?

jorgeajimenezl / aiodav

added replacement of aiohttp Connector via kwargs #4