Merge and squash pull request 78

Squashed commit of the following:

commit 2d9cc76bc5d11f164583810e4837abe4d25d8ff5
Author: Aaron Brown <aerizeon@gmail.com>
Date:   Sat Oct 11 20:20:16 2014 -0400

    Added callback and handling of Echo/Self messages from other steam client instances.

commit 9167ee7ef5935a5b3fc9d08ec4aa26d8ae85a727
Author: Aaron Brown <aerizeon@gmail.com>
Date:   Sat Oct 11 19:50:13 2014 -0400

    Added callback and handling of Echo/Self messages from other steam client instances.

Closes #78.

Signed-off-by: Netshroud <netshroud@gmail.com>
Refactor GetOSType, add WIndows 8/8.1
Update CS:GO, Dota 2 protobufs [ci skip]
Regen Dota 2 protobufs
Regen CS:GO protobufs
Merge branch 'master' of https://github.com/SteamRE/SteamKit