vm.$slots documentation improvement (#419)
vm.$slots documentation improvement (#419)

* vm.$slots documentation improvement

* vm.$slots doc fix: 'Render Function' instead of 'Render Functions'

* $vm.slots - improved initial sentence

* additional tweaks to vm. api entry

potato4d/jp.vuejs.org,potato4d/jp.vuejs.org,vuejs/jp.vuejs.org,vuejs/jp.vuejs.org