Feature update deprecation notes

[hardbyte]

So to use semantic versioning properly we need to bump the major version when our api changes in a backwards incompatible way.

The changes to the BusABC requiring custom backends to now implement _send_periodic_internal (not to mention all the other changes in the changelog) made me think we should be releasing 3.0 instead of 2.3

[felixdivo]

Sounds reasonable.

[christiansandberg]

I don’t think it should have been necessary to bump the major number. If an interface implements send_periodic method directly, everything should work just like it did before, right?

[felixdivo]

The changes to the mesaage class also break comparability in some ways.

[codecov]

Codecov Report

Merging #437 into develop will increase coverage by <.01%.
The diff coverage is 57.14%.

@@ Coverage Diff @@## develop #437 +/- ## ========================================== + Coverage 62.5% 62.5% +<.01%  ========================================== Files 55 55 Lines 4656 4657 +1 ========================================== + Hits 2910 2911 +1  Misses 1746 1746