Vigenere Cipher

Implement a Vigenere Cipher using JavaScript or Ruby. You should be able to encode and decode a word when given a keyword. Read the Wikipedia description here

A quick rundown of the steps:

1. You take the message you want to encrypt (in this case 'attackatdawn').

message: attackatdawn

2. You take the keyword you want to encrypt with (in this case 'lemon'), and repeat it so that it is the length as your message.

keyword: lemonlemonle

3. You add each letter of the message to each letter of the keyword to produce each letter of the ciphertext. For example, for the first letter:

• message: 'a' is index 0 in the alphabet
• keyword: 'l' is index 11 in the alphabet
• ciphertext: letter at index (0 + 11), which is 'l'

ciphertext: lxfopvefrnhr

TLDR: Write a function or method that takes two arguments. One argument must be the message you'd like to encrypt. The other argument should be the keyword. The output of that function or method should be the encrpyted message(ciphertext above)

Bonus: have the ability to decode an encrypted message with a keyword.