Use 'npm bin' to find the correct binaries

.travis.yml

@@ -15,11 +15,10 @@ before_install:
 - "if [ -d node_modules ] && [ x$(cat node_modules/.last-node-version 2>/dev/null) != x$(node -e 'console.log(process.version)') ]; then npm rebuild && node -e 'console.log(process.version)' > node_modules/.last-node-version; fi"
 before_script:
 - npm install web-component-tester bower polylint
-- bower install
-- polylint --no-recursion
-- export PATH=$PWD/node_modules/.bin:$PATH
+- $(npm bin)/bower install
+- $(npm bin)/polylint --no-recursion
 script:
-- xvfb-run wct
-after_success: '[ ${TRAVIS_PULL_REQUEST} = "false" ] && [ ${TRAVIS_BRANCH} = "master" ] && bower install -s https://${GH_TOKEN}@github.com/Collaborne/collaborne-build-tools.git && bower_components/collaborne-build-tools/gpages_build.sh Collaborne info@collaborne.com'
+- xvfb-run $(npm bin)/wct
+after_success: '[ ${TRAVIS_PULL_REQUEST} = "false" ] && [ ${TRAVIS_BRANCH} = "master" ] && $(npm bin)/bower install -s https://${GH_TOKEN}@github.com/Collaborne/collaborne-build-tools.git && bower_components/collaborne-build-tools/gpages_build.sh Collaborne info@collaborne.com'
 env:
   secure: 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