[S2GRAPH-233] Refactor EdgeFetcher, EdgeMutator to extend `RxStep`.

• Type: Sub-task
• Status: To Do
• Priority: Major
• Resolution: Unresolved
• Component/s: s2core
• Assignee: Unassigned
• Reporter: Do Yung Yoon
• Due: 27/Jul/18
• Created: 09/Jul/18 06:40
• Updated: 09/Jul/18 06:42

Description

Once the new `Step` interface is defined at S2GRAPH-229, It would be good to try refactoring `EdgeFetcher`, `EdgeMutator` to extends new interface.