Add Python 3 support

[sebdah]

Add Python 3 support

[webknjaz]

Ref: https://github.com/benjaminp/six

[lcz1688]

'dict' object has no attribute 'iteritems' after I update to the 0.11.0 in python3

[sebdah]

@lcz1688 please note that Python 3 support is not there in 0.11.0.

[fusionbeam]

please consider this pull request: #42