minor symfony#14613 [travis] Use container-based infrastructure (nicolas-grekas)

This PR was merged into the 2.3 branch.

Discussion
----------

[travis] Use container-based infrastructure

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Let's see if this works...

Commits
-------

2aea3aa [travis] Use container-based infrastructure

Author: nicolas-grekas

.travis.yml

@@ -1,5 +1,16 @@
 language: php
 
+sudo: false
+
+cache:
+  directories:
+    - $HOME/.composer/cache
+
+addons:
+  apt_packages:
+    - parallel
+    - language-pack-fr-base
+
 matrix:
     include:
         - php: 5.3.3
@@ -26,14 +37,12 @@ env:
         - SYMFONY_DEPRECATIONS_HELPER=weak
 
 before_install:
-    - travis_retry sudo apt-get install parallel
     - composer self-update
     - if [[ "$TRAVIS_PHP_VERSION" != "nightly" ]] && [[ "$TRAVIS_PHP_VERSION" != "hhvm" ]]; then phpenv config-rm xdebug.ini; fi;
     - if [[ "$TRAVIS_PHP_VERSION" != "nightly" ]] && [[ "$TRAVIS_PHP_VERSION" != "hhvm" ]]; then echo "extension = mongo.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini; fi;
     - if [[ "$TRAVIS_PHP_VERSION" != "nightly" ]] && [[ "$TRAVIS_PHP_VERSION" != "hhvm" ]] && [ $(php -r "echo PHP_MINOR_VERSION;") -le 4 ]; then echo "extension = apc.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini; fi;
     - if [[ "$TRAVIS_PHP_VERSION" != "nightly" ]] && [[ "$TRAVIS_PHP_VERSION" != "hhvm" ]]; then (pecl install -f memcached-2.1.0 && echo "extension = memcache.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini) || echo "Let's continue without memcache extension"; fi;
     - if [[ "$TRAVIS_PHP_VERSION" != "nightly" ]] && [[ "$TRAVIS_PHP_VERSION" != "hhvm" ]]; then php -i; fi;
-    - sudo locale-gen fr_FR.UTF-8 && sudo update-locale
     # Set the COMPOSER_ROOT_VERSION to the right version according to the branch being built
     - if [ "$TRAVIS_BRANCH" = "master" ]; then export COMPOSER_ROOT_VERSION=dev-master; else export COMPOSER_ROOT_VERSION="$TRAVIS_BRANCH".x-dev; fi;