fix use of "$COMPOSER" instead of composer.json in a few spots
fix use of "$COMPOSER" instead of composer.json in a few spots

rs-makino/buildpack-test,dzuelke/heroku-buildpack-php,wzrdtales/heroku-buildpack-php,rs-makino/buildpack-test,emeth-/heroku-buildpack-php,martijngastkemper/heroku-buildpack-php,alzheic/heroku-buildpack-aop,emeth-/heroku-buildpack-php,0ppy/sample-buildpack,jopereyral/heroku-buildpack-php,jayelkaake/heroku-buildpack-magento,dzuelke/heroku-buildpack-php,createmultimedia/heroku-buildpack-php,alzheic/heroku-buildpack-aop,rikur/heroku-buildpack-php,rs-makino/buildpack-test,rikur/heroku-buildpack-php,heroku/heroku-buildpack-php,puteulanus/heroku-buildpack-php,emeth-/heroku-buildpack-php,rs-makino/buildpack-test,alzheic/heroku-buildpack-aop,jopereyral/heroku-buildpack-php,jayelkaake/heroku-buildpack-magento,flant/heroku-buildpack-php,thecsea/heroku-buildpack-php-with-ioncube,Apelsin/heroku-buildpack-phabricator,wzrdtales/heroku-buildpack-php,thecsea/heroku-buildpack-php-with-ioncube,0ppy/sample-buildpack,puteulanus/heroku-buildpack-php,createmultimedia/heroku-buildpack-php,a2service/heroku-buildpack-php,rs-makino/buildpack-test,createmultimedia/heroku-buildpack-php,rikur/heroku-buildpack-php,rikur/heroku-buildpack-php,heroku/heroku-buildpack-php,a2service/heroku-buildpack-php,heroku/heroku-buildpack-php,a2service/heroku-buildpack-php,emeth-/heroku-buildpack-php,rs-makino/buildpack-test,Apelsin/heroku-buildpack-phabricator,jayelkaake/heroku-buildpack-magento,thecsea/heroku-buildpack-php-with-ioncube,flant/heroku-buildpack-php,martijngastkemper/heroku-buildpack-php,0ppy/sample-buildpack,flant/heroku-buildpack-php,puteulanus/heroku-buildpack-php,jopereyral/heroku-buildpack-php,dzuelke/heroku-buildpack-php,heroku/heroku-buildpack-php