Drop support for Py27

[scasagrande]

The time is coming near! Py27 is finally reaching EOL in ~1 year. I want to have Py27 support removed for the v1.0 version.

This issue will contain a list of things that will need to be done to go with this. This list isn't finalized, and might expand as time goes.

• Remove from __future__ import X statements
• Remove inheritance from object
• Remove enum34 package
• Change setup.py to indicate only Py3 is supported
• Update documentation to mention only Py3 is supported
• Change class definitions that utilize metaclasses to use the Py3 specific syntax (metaclass= instead of using future.utils.with_metaclass)

[jaron-l]

I know I'm early to the game but Python support for 2.7 stopped yesterday. Currently enum34 is breaking pyinstaller so when enum34 is removed, instrumentkit can work with pyinstaller theoretically.

[scasagrande]

Oh interesting

And don't worry, you're not early lol. I was cracking the whip today on everyone at work, so now its my turn for myself.

[scasagrande]

@jaron-l I've removed enum34 on master so feel free to give that a try