Merge pull request #114 from hcpl/minimal-versions

Test with `-Z minimal-versions` on CI

.travis.yml

@@ -8,11 +8,17 @@ rust:
 before_script:
   - pip install 'travis-cargo<0.2' --user && export PATH=$HOME/.local/bin:$PATH
 script:
+  - if [ "${MINIMAL_VERSIONS}" = "y" ]; then cargo update -Z minimal-versions; fi
   - cargo run -p ci
   - cargo run --example default
 after_success:
   - travis-cargo --only nightly doc-upload
 
+matrix:
+  include:
+    - rust: nightly
+      env: MINIMAL_VERSIONS=y
+
 notifications:
   email:
 on_success: never