Fix missing Helper method in edit and use $EDITOR

* Fix the missing Helper method in the edit command to use Helper.HOME and the correct path assembly method (path.join) instead of joining strings together!
* Use $EDITOR instead of "vi" in the event a user doesn't have "vi" installed or doesn't understand it. Fallback to "vi" in case user doesn't have $EDITOR set.

src/command-line/edit.js

@@ -15,8 +15,8 @@ program
 			return;
 		}
 		child.spawn(
-			"vi",
+			process.env.EDITOR || "vi",
-			[Helper.resolveHomePath("users", name, "user.json")],
+			[require("path").join(Helper.HOME, "users", name, "user.json")],
 			{stdio: "inherit"}
 		);
 	});