Feature request: add support for unix domain socket

Just discovered the project. This looks really nice.

go grpc implementation supports unix sockets. I wanted to know if you would consider adding support in evans as well.

From what I see it is already almost working if we set as an address unix:///path/to/socket. evans already tries to connect via the unix socket protocol but the only issue seems to be that evans concatenate the port no matter what

As a consequence the file name is wrong and evans cannot connect (I guess that it could work if the socket was awkwardly named like socket:123 😅)

I could get it to work by not adding the :<port> part if the address starts with unix://, so the fix looks simple (but there are other things to do for completeness, probably to add tests and change the prompt in the repl).

I can try to work on it and open a PR if you are interested (I'm not very familiar with go and the project itself, so if someone else is faster than me even better).