Support for dockerized RPC clients + Hostname resolution when attaching to RPC clients

[mariuspod]

What I did

I've extended the check that is determining if a RPC client is already running to also query the network connections in addition to the process list. The error I've observed on a Ubuntu 18.04 LTS was that only localhost RPC clients could be detected with the existing code. Even dockerized RPC clients bound to the 127.0.0.1 could not be attached.

How I did it

I've adapted the logic to first try the process list and then the network connections.
I've also implemented hostname resolution which becomes handy when the RPC client is bound to a specific hostname instead of IP which is often the case when used in docker-compose environments.

How to verify it

docker run -p 8545:8545 trufflesuite/ganache-cli

Then in another terminal

brownie console

Checklist

• I have confirmed that my PR passes all linting checks
• I have included test cases
• I have updated the documentation
• I have added an entry to the changelog

[iamdefinitelyahuman]

I think this fixes #371

[iamdefinitelyahuman]

Very cool, thanks for your contribution