Signatures of Recipient::do_send() and Addr::do_send() are not consistent

[hoodie]

Expected Behavior

Recipient::do_send() should not return a Result, same as Addr::do_send() does.

Current Behavior

Currently Recipient::do_send() is identical in behavior with Recipient::try_send(), this seems to be an oversight.

Possible Solution

Consume the Result inside the method body, same as Addr::do_send() does:
https://github.com/actix/actix/blob/master/src/address/mod.rs#L99

Context

This is a breaking API change, but a consistency improvement, users of Recipient::do_send() presumably already throw away the Result.