Please mention in documentation in what version of the unity API a field/property/class was made deprecated/obsolete or added/changed/removed. E.g. I found that onValueChange has been renamed to onValueChanged, but I have no idea in which version this change happened, which means I have to test my editor extension in 10+ different versions (4.6-5.3) to find out.
This extra information would make it easier for us editor extension developers that need to keep our stuff backwards compatible.
Another solution is to make a compact searchable change-log available (containing changes for all unity versions). It will work if the change-log is detailed enough to contain small changes such as the one mentioned above.