.travis.yml: Really run quickcheck_macros tests on nightly

Signed-off-by: Anders Kaseorg <[email protected]>

Author: andersk

.travis.yml

@@ -7,7 +7,7 @@ script:
   - cargo build --verbose
   - cargo test --verbose
   - cargo doc
-  - if [ "$TEST_SUITE" = "suite_nightly" ]; then
+  - if [ "$TRAVIS_RUST_VERSION" = "nightly" ]; then
       cargo build --verbose --manifest-path quickcheck_macros/Cargo.toml;
       cargo test --verbose --manifest-path quickcheck_macros/Cargo.toml;
     fi