Revert "Merge branch 'jest'"

This reverts commit f76e9e108f.

caesar/README.md

@@ -1,6 +1,6 @@
-# Exercise 13 - Caesar cipher
+# Exercise XX - caesar cipher
 
-Implement the legendary Caesar cipher:
+Implement the legendary caesar cipher:
 
 > In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caesar, who used it in his private correspondence.
 
@@ -31,3 +31,5 @@ negative numbers should work as well:
 ```javascript
 caesar('Mjqqt, Btwqi!', -5) // returns 'Hello, World!'
 ```
+
+