timing out while calling Socket.web.recv with timeout raises exception

When calling recv like this:
```
Socket.Web.recv(connection, [timeout: 100])
```
and a timeout happens, this exception is raised:
```
** (CaseClauseError) no case clause matching: {:error, :timeout}
    (socket) lib/socket/web.ex:666: Socket.Web.recv/2
```

socket version: 0.3.12
elixir version: 1.6.1