Feature request: add a wrapper to get conversation history

[asinghvi17]

I'd like to be able to back up a couple of private channels, perhaps posting them on Github.

https://api.slack.com/methods/conversations.history#response shows that this is possible, with a little effort :D. If you can provide the API endpoint, I could do the rest.

[logankilpatrick]

I will have this done soon. I haven't had time until yesterday's hackathon and it's almost complete.

b366acf

[logankilpatrick]

This is possible now @asinghvi17