Add python3 support

[kwauchope]

Have a fork based on work from @mpern port to python3 but with the latest code base.

Changes include map as iter, subscript in lambda functions, print as a function and Exception syntax. All of these have been back ported and are compatible with 2.6 and 2.7. Current travis ci build succeeds on 2.6,2.7,3.2,3.3,3.4.