Proposal for Stretch package versioning

[WasabiFan]

I'd like to propose the following versioning scheme for future releases targeting ev3dev-stretch.

I think we should leave v1.y.z as-is to target Jessie for any future work, and release Stretch versions starting at v2.0.0. Given that it's looking like our first Stretch release will include reasonably large changes from v1.0.0 and, more importantly, some breaking API changes, starting at 2.0.0 will make the significance clear.

Thoughts?

[WasabiFan]

2.0.0-beta1 has been released to the Debian package server and PyPi.