v0.7.0

⚠️ 0.7.x will be the final feature release that will support Python 2.7 and 3.5

• Adds urls package.
• Adds type information to endpoints.
• bc3 configure now prompts user to select an account ID if they
    belong to multiple Basecamp3 accounts.
• Changes Docker container to use slim instead of alpine
• Python 2 imports wrapped in try/catch are replaced with six.moves
    instead.

Full Changelog: v0.6.1...v0.7.0