update fuel install.sh to work with updated composer install process

frameworks/PHP/fuel/install.sh

@@ -1,12 +1,13 @@
 #!/bin/bash
 
 export PHP_HOME=${IROOT}/php-5.5.17
+export COMPOSER_HOME=${IROOT}/php-composer
 export PHP_FPM=$PHP_HOME/sbin/php-fpm
 export NGINX_HOME=${IROOT}/nginx
 
 
 fw_depends php nginx composer
 
-${PHP_HOME}/bin/php $IROOT/composer.phar install \
+${PHP_HOME}/bin/php $COMPOSER_HOME/composer.phar install \
   --no-interaction --working-dir $TROOT \
   --no-progress --optimize-autoloader