Implemented runes

src/build/errors/NumberExceedsBounds.go

@@ -0,0 +1,15 @@
+package errors
+
+import "fmt"
+
+// NumberExceedsBounds error is created when the number doesn't fit into the destination.
+type NumberExceedsBounds struct {
+	Number       int
+	Size         byte
+	ExpectedSize byte
+}
+
+// Error generates the string representation.
+func (err *NumberExceedsBounds) Error() string {
+	return fmt.Sprintf("Number %d needs %d bytes but the maximum is %d bytes", err.Number, err.Size, err.ExpectedSize)
+}