remove heroku since we've long had the pitometer script commented out

Author: jpolitz

.travis.yml

@@ -9,11 +9,9 @@ node_js:
 install:
 - npm update
 - make install
-- npm install -g heroku
 before_script:
 - make
 script:
-# - if [ "$TRAVIS_PULL_REQUEST" = "false" ]; then heroku run:detached --size=performance-m --app pyret-pitometer node bench/run.js --commit $TRAVIS_COMMIT --repo https://github.com/brownplt/pyret-lang/; fi
 - make all-pyret-test
 notifications:
   slack: