Adding Armstrong Number in CoffeeScript

[Geeky-star]

Fixes #2120

Checklist:

• [x] 4 space indentation.
• [x] Coding conventions are followed.
• [x] Input is taken dynamically.
• [x] Sample Input / Output is added at the end of file.
• [x] Logic Documentation (Comments).
• [x] File names are correct.

Make sure these boxes are checked before your pull request (PR) is ready to be reviewed and merged. Thanks!

Changes proposed in this pull request:

• Added Armstrong Number in CoffeeScript

Languages Used:

• CoffeeScript

Files Added:

• Armstrong_Number.coffee

We're happy to help you get this ready -- don't be afraid to ask for help.

Thanks!