Update .travis.yml

.travis.yml

@@ -11,20 +11,18 @@ rust:
   - beta
   - nightly
 before_script:
-  # load travis-cargo
   - pip install 'travis-cargo<0.2' --user
   - export PATH=$HOME/.local/bin/:$PATH
-# the main build
 script:
   - travis-cargo build
   - travis-cargo test
   - travis-cargo bench
   - travis-cargo --only stable doc
 after_success:
-  # upload the documentation from the build with stable (automatically only
-  # actually runs from the master branch, not individual PRs)
   - travis-cargo --only stable doc-upload
-  # measure code coverage and upload to coveralls.io (the verify argument
-  # mitigates kcov crashes due to malformed debuginfo, at the cost of some
-  # speed. <https://github.com/huonw/travis-cargo/issues/12>)
   - travis-cargo coveralls --no-sudo --verify
+
+
+env:
+  global:
+    - TRAVIS_CARGO_NIGHTLY_FEATURE=nightly