Complex topics trigger a Protocol.UndefinedError

[stmichael]

Thanks for this small but useful library. I write something very similar of my own and thought about publishing it. But then I stumbled upon your project which completely satisfies my needs.

I came across an issue. I need to have more complex topics than just plain string. Unfortunately that produced an error:

[error] an exception was raised:
    ** (Protocol.UndefinedError) protocol String.Chars not implemented for {"job", 155}
        (elixir) lib/string/chars.ex:3: String.Chars.impl_for!/1
        (elixir) lib/string/chars.ex:17: String.Chars.to_string/1
        (pg2pubsub) lib/pg2pubsub.ex:29: Pg2PubSub.subscribe/1
        (thumbs_up_ui) web/channels/job_channel.ex:7: ThumbsUpUi.JobChannel.join/3
        (phoenix) lib/phoenix/channel/server.ex:169: Phoenix.Channel.Server.init/1
        (stdlib) gen_server.erl:328: :gen_server.init_it/6
        (stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3

Here is a fix to this problem 😄

[kbremner]

Glad it's of some use! I wrote it to try out PG2 but if it's useful then that's good to hear :)

Thanks for the PR, just 2 things. Could you update the spec statements, now that the methods can accept something other than strings, and could you add doc tests showing the use of a non-string topic?

If you could make those changes, I can get this merged!

[stmichael]

Sorry, I forgot about that. How about now?