Update to Rust 1.35.0. (#83)

.travis.yml

@@ -1,6 +1,6 @@
 language: rust
 rust:
-    - 1.33.0
+    - 1.35.0
 cache:
   cargo: true
   timeout: 1200

src/mock/ms8.rs

@@ -434,7 +434,7 @@ mod tests {
     // otherwise unusual expressions, so the lint is disabled.
     #![allow(clippy::eq_op)]
     // Some test functions contain long lists of assertions. Clippy thinks they are too complex.
-    #![allow(clippy::cyclomatic_complexity)]
+    #![allow(clippy::cognitive_complexity)]
 
     use super::{ext_euclid, modular_pow, Mersenne8};
     use pairing::Field;