Add encrypting cookier
Add helper constructor to create SecureCookier
Change to base64 encoded secret for SecretCookier

Also changes from HmacSHA1 to HmacSHA256
Add main program to generate encrypt and hmac keys
Merge pull request #1 from mdietz198/master

Change SecretCookier to HmacSHA256 with base64 encoded key and add EncryptingCookier