deps: Update to a more recent rocket and rust toolchain

With this patch, Plume will be use a more up-to-date revision of
Rocket, that works with nightly-2018-07-17. It may have been able to
make it work with a more recent revision, but it turns out rocket has
introduced several breaking changes so I’d rather fix those.

Besides updating rocket_i18n and rocket_csrf to use the same revision
than Plume, this patch deals with the new implementation of the
Uri<'_> type. It silents a class of warnings, to deal with a change in
rustc which affects diesel. This latter change should be reverted as
soon as diesel releases a new version of its crate.

src/setup.rs

@@ -170,7 +170,7 @@ fn quick_setup(conn: DbConn) {
         .output()
         .map(|o| String::from_utf8(o.stdout).expect("Invalid output from openssl"))
         .expect("Couldn't generate secret key.");
-    write_to_dotenv("ROCKET_SECRET_KEY", key);    
+    write_to_dotenv("ROCKET_SECRET_KEY", key);
 
     create_admin(instance, conn);
 }