Add history/changelog to readme

[FGRibreau]

... and specify that bo-for was removed between 0.1.1 and 0.2.1, the work-around is to replace bo-for by bo-attr bo-attr-for.

[Pasvaz]

A changelog would be neat, however as long as I remember bo-for never existed.

[FGRibreau]

You're right, I forgot I added bo-for myself :)

[Pasvaz]

I guess it was a sort of cycle/repeater, if you think other can take benefit from it, feel free to commit it.