[feature request] add `fillstruct` to gosublime

[maplebed]

The fillstruct command (https://godoc.org/github.com/davidrjenni/reftools/cmd/fillstruct) is super useful and amazing. It'd be lovely to have an option or mode where when you auto-complete a struct in assignment it autopopulates all the members of the struct. (tab-complete on members of the struct already works, so maybe this isn't too far out?)