graph-tool 2.29 breaks backward compatibility

Hello folks,

I've discovered, while trying to fix and 'never seen before bug', after
having installed graph-tool 2.29 from a Ubuntu repo, that some new
features was not backward compatible.

For example, my error came from that fact that now, the function
`get_edges` returns by default a `Nx2` matrix, whereas it used to return
a `Nx3` matrix in prior version.

After a quick search on the doc, changelog and mailing list, I didn't
find mention of these changes, so I am wandering if there is a place to
find such information, and if there may be other changes that affect the
backward compatibility in new version ?