Add ownProps to mapStateToProps and mapDispatchToProps as second parameter

[gaearon]

It should only be passed if fn.length > 1 as per #36 (comment).

If you want to make a PR, please write here so we don't duplicate effort.

[gaearon]

Important note: if mapDispatchToProps.length < 2, mapDispatchToProps should not be called on prop change.

Similarly, if mapStateToProps.length < 2 or mergeProps.length < 3, componentWillReceiveProps should not result in their recalculation, respectively.

[gaearon]

cc @jhollingworth, @danharper, @ForbesLindesay who wanted to make this happen

[jhollingworth]

Happy to implement this if no one else is

[gaearon]

Feel free to!

[PSpSynedra]

@Gaeron What is the current state of this issue?
We were just updating to redux 1.0.x and have serious problems with props not being available to mapStateToProps. The reason is that we pass memoized selector functions via props that select the desired childProperties from the state.
As a workaround we could select the whole state and thus have it passed to the mergeProps callback. The problem using this workaround is, that the potentionally expensive mergeProps becomes the mapStateToProps and is callled much to often (the recomputeState is actually called for every state change in the redux store, no matter what part of the state was influenced by the change).

[imevro]

@PSpSynedra #59 (comment)

[PSpSynedra]

@theaqua, Yeah I just saw it :-) Looking forward to it already.