python 3 compatibility, TE combo flag, remove duo flag

[sharkiteuthis]

• python3 compatibility changes
• Changes to make tests more robust
• Added salary minimum constraint (no flag yet)
• Added combo_allow_te switch to allow QB/TE combo (see #86)
• Removed duo and dtype flags since there was no implementation

[BenBrostoff]

This is awesome @sharkiteuthis ; I'll review today and over weekend. My biggest concern here is maintaining the Docker setup and ensuring Travis build still works. These changes look great.

I would also mention that you should check out this issue about converting this repo to accommodate a pip module and separating the CLI and optimize.run functionality.

I have a lot of scripts I run for various DraftKings / FanDuel contests that submodule this repo; I know others are using the setup that is in examples. This is less flexible than a pip module that can just be dropped into an existing project. Let me know if you have ideas here; I mention this just because this refactor is going to change a lot of the code. That said, I want to get your work merged in first 👍

[BenBrostoff]

Alright, final things here @sharkiteuthis :

• If you're good with my changes, merge this PR
• Change the README to indicate this is only for Python 3.6+ now

[BenBrostoff]

I think build is failing because of some linting flake8 thing, so if you don't mind fixing, I'll merge once it's passing.

[sharkiteuthis]

working now, added a missing package for tests