travis: remove commented out code. (#828)

The commented out lines are no longer relevant and will not be brought
back.

.travis.yml

@@ -80,11 +80,6 @@ script: |
       cargo check --tests --all --exclude tokio-tls --target $TARGET
   else
       cargo test --all --no-fail-fast
-      # Disable these tests for now as they are buggy
-      #
-      # cargo test --features unstable-futures
-      # cargo test --manifest-path tokio-threadpool/Cargo.toml --features unstable-futures
-      # cargo test --manifest-path tokio-reactor/Cargo.toml --features unstable-futures
   fi
 
 before_deploy: