It is worth noting that Caesar ciphers are vulnerable to a wide range of cryptanalysis methods, especially frequency analysis and statistical attacks, and should not be used for protection of sensitive data.

Instead, use something like RSA/AES for this.

Still, very nice work. Always good to see people learning about cryptography. 
Perhaps for a next project you could consider writing software that implements some attacks on a Caesar cipher to demonstrate why they should not be used for protecting sensitive data?

Links:  
[Practical Cryptography - Cryptanalysis of Caesar Cipher](http://practicalcryptography.com/cryptanalysis/stochastic-searching/cryptanalysis-caesar-cipher/)  
[Wikipedia on Breaking a Caesar Cipher](https://en.wikipedia.org/wiki/Caesar_cipher#Breaking_the_cipher)