challenge: do challenge 5

* challenge/c05.go: Implement challenge 5.
* cryptopals.go (main): Add handling to run challenge 5.
* lib/hex.go (BytesToHexStr): New function.
* lib/xor.go (RepeatingXOR): New function.

1 files changed, 2 insertions, 0 deletions

diff --git a/cryptopals.go b/cryptopals.go
index 671564b..0d0a557 100644
--- a/cryptopals.go
+++ b/cryptopals.go
@@ -26,5 +26,7 @@ func main() {
 		challenge.C3()
 	case 4:
 		challenge.C4()
+	case 5:
+		challenge.C5()
 	}
 }