Build benches in TravisCI

Author: kpp

.travis.yml

@@ -6,15 +6,14 @@ rust:
 os:
   - linux
 
-script:
-  - cargo test
-
 matrix:
   include:
     - os: linux
-      rust: nightly-2019-08-21
+      script:
+        - cargo build --examples --tests --benches
+    - name: coverage
+      os: linux
       sudo: required
-      name: coverage
       addons: # needed for `cargo install cargo-travis`
         apt:
           packages: