minor #537 Use the newer stack for HHVM on Tracis CI (bocharsky-bw)
minor #537 Use the newer stack for HHVM on Tracis CI (bocharsky-bw)

This PR was squashed before being merged into the master branch (closes #537).

Discussion
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Use the newer stack for HHVM on Tracis CI

Commits
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8bdcc66 Use the newer stack for HHVM on Tracis CI

voronkovich/symfony-demo,javiereguiluz/symfony-demo,dzuelke/symfony-demo,Codeception/symfony-demo,yceruto/symfony-demo,yceruto/symfony-demo,voronkovich/symfony-demo,yodur2potassium/test-behat-selenium-symfo,TomasVotruba/symfony-demo,bocharsky-bw/symfony-demo,dzuelke/symfony-demo,symfony/symfony-demo,Codeception/symfony-demo,TomasVotruba/symfony-demo,bocharsky-bw/symfony-demo,TomasVotruba/symfony-demo,symfony/symfony-demo,yceruto/symfony-demo,dzuelke/symfony-demo,Codeception/symfony-demo,voronkovich/symfony-demo,javiereguiluz/symfony-demo,symfony/symfony-demo,yodur2potassium/test-behat-selenium-symfo,bocharsky-bw/symfony-demo,yodur2potassium/test-behat-selenium-symfo,javiereguiluz/symfony-demo