Fixed save & restore

[elie-g]

I did the following in the same order:

1. I changed the name of the constant containing the CSI (ESC) to the appropriate name (CSI).
2. Created a new constant named ESC containing only the ANSI escape character.
3. Fixed save & restore by using the ESC constant instead of CSI
4. Added tests for save & restore
5. Ran the tests (69/69 passed)

NOTE:
I noticed that both constants clear and beep in index.js are exactly the same. Is this intended?
Both of them are exported.

[elie-g]

I check the ASCII table and the 7th character (\u0007) is the bell so idk if clear is used anywhere but I really doubt it clears anything.

[terkelg]

Maybe I meant clearScreen as here: https://github.com/sindresorhus/ansi-escapes/blob/master/index.js#L83. But I think it's safe to remove for now