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/routes/posts.rs

@@ -75,7 +75,10 @@ fn activity_details(blog: String, slug: String, conn: DbConn, _ap: ApRequest) ->
 
 #[get("/~/<blog>/new", rank = 2)]
 fn new_auth(blog: String) -> Flash<Redirect> {
-    utils::requires_login("You need to be logged in order to write a new post", uri!(new: blog = blog))
+    utils::requires_login(
+        "You need to be logged in order to write a new post",
+        uri!(new: blog = blog).into()
+    )
 }
 
 #[get("/~/<blog>/new", rank = 1)]