Fix rustc warnings

New warnings were introduced with rustc 1.29.0

podcasts-data/src/lib.rs: this one can be removed once diesel is
upgraded.
https://github.com/diesel-rs/diesel/issues/1785#issuecomment-422577018

podcasts-gtk/src/i18n.rs: This is just a deprication warning

podcasts-data/src/lib.rs

@@ -45,6 +45,7 @@
     elided_lifetime_in_paths,
     missing_copy_implementations
 )]
+#![allow(proc_macro_derive_resolution_fallback)]
 #![deny(warnings)]
 
 //! FIXME: Docs

podcasts-gtk/src/i18n.rs

@@ -21,7 +21,7 @@ fn kreplace(input: String, kwargs: &[(&str, &str)]) -> String {
     for (k, v) in kwargs {
         if let Ok(re) = Regex::new(&format!("\\{{{}\\}}", k)) {
             s = re
-                .replace_all(&s, |_: &Captures| v.to_string().clone())
+                .replace_all(&s, |_: &Captures<'_>| v.to_string().clone())
                 .to_string();
         }
     }