Secure OAuth Token

Fixes #24

 * In Production, force ssl
 * Add MyGists::Secure with .encrypt and .decrypt class methods
   * Encoded token should be utf8 for PostgreSQL
 * Add profiles.token to persist OAuth token from GitHub
 * After authenticating with GitHub, save the passed back token
 * Only set GitHub avatar into users session
 * Overload Profile#token to respond with decrypted token
 * Remove ProfileDecorator#token, so Profile model can respond to the message