Added caesar cipher algorithm (#13)

Author: adam-pog

ciphers/CaesarCipher.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"strings"
+)
+
+func main() {
+	cipherKey := flag.Int("c", 0, "Cipher shift amount (-26 - 26)")
+	input := flag.String("i", "", "Input")
+	flag.Parse()
+
+	if *cipherKey > 26 || *cipherKey < -26 {
+		flag.PrintDefaults()
+	} else {
+		fmt.Println(caesarCipher(*input, *cipherKey))
+	}
+
+}
+
+func caesarCipher(input string, key int) string {
+	var outputBuffer bytes.Buffer
+	for _, r := range strings.ToLower(input) {
+		newByte := int(r)
+
+		if newByte >= 'a' && newByte <= 'z' {
+			newByte += key
+
+			if newByte > 'z' {
+				newByte -= 26
+			} else if newByte < 'a' {
+				newByte += 26
+			}
+		}
+
+		outputBuffer.WriteString(string(newByte))
+	}
+	return outputBuffer.String()
+}