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.

plume-common/src/utils.rs

@@ -17,7 +17,7 @@ pub fn make_actor_id(name: String) -> String {
 }
 
 pub fn requires_login(message: &str, url: Uri) -> Flash<Redirect> {
-    Flash::new(Redirect::to(Uri::new(format!("/login?m={}", gettext(message.to_string())))), "callback", url.as_str())
+    Flash::new(Redirect::to(format!("/login?m={}", gettext(message.to_string()))), "callback", url.to_string())
 }
 
 /// Returns (HTML, mentions)