Apply emphasis to the important parts of the README

README.md

 encbook
 ===
 
-CardDAV server with per-user encryption of the data.
+CardDAV server with per-user encryption of the data (prototype).
 
 Data is stored in a separate encrypted SQLite database (using
 [sqleet](https://github.com/resilar/sqleet)) for each user, so that we
@@ -9,8 +9,8 @@ can encrypt it with a user-specific key. The user-specific key should
 be a long-term key that can be itself decrypted using the user
 password; eventually a
 [service](https://git.autistici.org/id/keystore) could be used to
-provide it. Since this is just a prototype, there is no authentication
-and the encryption key is just the user's password.
+provide it. **Since this is just a prototype, there is no authentication
+and the encryption key is just the user's password.**
 
 ## Usage