Create caesarcipher.py (#306)

* Create caesarcipher.py

This is a simple example of a Caesar Cipher for Hacktoberfest- this is my first-ever pull request! :)

* Updated README to include program in list

README.md

@@ -41,7 +41,8 @@ More information on contributing and the general code of conduct for discussion
 | Autocomplete Notes App                           | [AutoCert](https://github.com/DhanushNehru/Python-Scripts/tree/master/Autocomplete%20Notes%20App)                                                               | A Python script to auto-generate e-certificates in bulk.                                                            |
 | Automated Emails                     | [Automated Emails](https://github.com/DhanushNehru/Python-Scripts/tree/master/Automate%20Emails%20Daily)                                            | A Python script to send out personalized emails by reading a CSV file.                                              |
 | Black Hat Python                            | [Black Hat Python](https://github.com/DhanushNehru/Python-Scripts/tree/master/Black%20Hat%20Python)                                                             | Source code from the book Black Hat Python                                                           |
-| Blackjack                            | [Blackjack](https://github.com/DhanushNehru/Python-Scripts/tree/master/Blackjack)                                                             | A game of Blackjack - let's get a 21.                                                                               |
+| Blackjack                            | [Blackjack](https://github.com/DhanushNehru/Python-Scripts/tree/master/Blackjack)                                                             | A game of Blackjack - let's get a 21. 
+|Caesar Cipher                         | [Caesar Cipher](https://github.com/rusty-bytes7/Python-Scripts/blob/e94c8b52d313dc0d66b9ed0b55032c4470f72475/caesarcipher.py)                                                             | A Python script to encrypt messages using the Caesar cipher.                                          |
 | Chessboard                           | [Chessboard](https://github.com/DhanushNehru/Python-Scripts/tree/master/Chess%20Board)                                                        | Creates a chessboard using matplotlib.                                                                               |
 | Compound Interest Calculator         | [Compound Interest Calculator](https://github.com/DhanushNehru/Python-Scripts/tree/master/Calculate%20Compound%20Interest)                    | A Python script to calculate compound interest.                                                                     |
 | Countdown Timer                      | [Countdown Timer](https://github.com/DhanushNehru/Python-Scripts/tree/master/Countdown%20Timer)                                               | Displays a message when the Input time elapses.                                                                     |

caesarcipher.py

@@ -0,0 +1,21 @@
+#this program is a simple caesar cipher, which encrypts
+#a message by shifting each letter three to the right in the alphabet
+#this will ignore all characters that are not letters
+
+def caesar_encrypt(plaintext):
+    #each letter in plaintext
+    finalstring= ""
+    for letter in plaintext.lower():
+        #get the number value of the letter
+        cipher = (ord(letter)+3)
+        #wraparound
+        #checks letter to see if it's out of range
+        if cipher > 122:
+            cipher -= 26
+            finalstring += chr(cipher)
+        #skips any other characters
+        elif (ord(letter)) in range (97,123):
+            finalstring +=chr(cipher)
+        else: 
+            continue
+    return(finalstring)