need fetch "from" state not just the "to" state

[zppro]

i think it's necessary to add get from state info like beforeRouteEnter (from,to,next) now we can fetch the to state by store.route but some times to a view we must decide wether or not load data by the from state's path.
i.e. go to a product-details view from product-list view need loading details info and in that product-details view go to anther order view and back ,some contents managed by vuex had changed,so in details view i don't want load data because not necessary)

[predhme]

#36 Is a proposed changed to support storing the from transition in state.route

[yyx990803]

done by merging #36, now out in 4.0