would be great if merged.

But only works, if rtmbot.py is changed at beginning:

import sys
sys.dont_write_bytecode = True
+reload(sys)
+sys.setdefaultencoding('utf8')

+1
But in master branch, this code is moved to rtmbot/core.py. So I think modify this position which is
https://github.com/slackhq/python-rtmbot/blob/master/rtmbot/core.py#L104.

Turns out this was somewhat complicated to make it work in both py2.7 and py3.5. I think I have a solution in #46. Feel free to give it a look and add comments if you'd like.