horse: improve single target ahead/behind skills wording

Fixes #28.

skill.go

@@ -122,6 +122,15 @@ func (a Ability) String() string {
 		case 4:
 			r = append(r, " End Closer"...)
 		}
+	case TargetAhead, TargetBehind:
+		r = append(r, " to "...)
+		if a.TargetValue == 1 {
+			r = append(r, "the runner"...)
+		} else {
+			r = strconv.AppendInt(r, int64(a.TargetValue), 10)
+		}
+		r = append(r, ' ')
+		r = append(r, a.Target.String()...)
 	default:
 		// For other targeting types, TargetValue is either irrelevant or limit.
 		r = append(r, " to "...)
@@ -208,8 +217,8 @@ const (
 	TargetSympathizers  AbilityTarget = 2  // others with Sympathy
 	TargetInView        AbilityTarget = 4  // others in view
 	TargetFrontmost     AbilityTarget = 7  // frontmost
-	TargetAhead         AbilityTarget = 9  // others ahead
-	TargetBehind        AbilityTarget = 10 // others behind
+	TargetAhead         AbilityTarget = 9  // ahead
+	TargetBehind        AbilityTarget = 10 // behind
 	TargetAllTeammates  AbilityTarget = 11 // all teammates
 	TargetStyle         AbilityTarget = 18 // using style
 	TargetRushingAhead  AbilityTarget = 19 // rushing others ahead