Fix coding styles#85

Merged

sgkim126 merged 3 commits intoCodeChain-io:masterfrom

Jan 6, 2020

Commits on Jan 5, 2020

Remove extern crate statements
Seulgi Kim
committed

Commits on Jan 6, 2020

Reorder imports
Seulgi Kim
committed
Use the placeholders for elided lifetimes
Seulgi Kim
committed