Add bisect utility

This is too common of an optimization to not have this readily accessible. And I kinda like how this worked out, too. Go is fun.

days/14.go

@@ -104,26 +104,10 @@ func (d *Day14) Part1() string {
 func (d *Day14) Part2() string {
 	oreAvailable := int64(1000000000000)
 	estimate := oreAvailable / d.getOreRequiredForFuel(1)
-
-	high := estimate * 2
-	low := estimate
-
-	lastSuccess := low
-	lastFailure := high
-	fuelProduced := low
-
-	for math.Abs(float64(lastFailure-lastSuccess)) > 1 {
-		oreConsumed := d.getOreRequiredForFuel(fuelProduced)
-		adjustment := (lastFailure - lastSuccess) / 2
-		if oreConsumed < oreAvailable {
-			lastSuccess = fuelProduced
-		} else {
-			lastFailure = fuelProduced
-			adjustment = -adjustment
-		}
-
-		fuelProduced += adjustment
-	}
+	lastSuccess := u.Bisect(estimate, estimate*2, 1, func(val int64) bool {
+		oreConsumed := d.getOreRequiredForFuel(val)
+		return oreConsumed < oreAvailable
+	})
 
 	return fmt.Sprintf("Maximum fuel we can make from 1 trillion ore: %s%d%s", u.TextBold, lastSuccess, u.TextReset)
 }