minor #1007 Add symfony 4.4 and 5.0 to .travis.yml (Mazarini)
minor #1007 Add symfony 4.4 and 5.0 to .travis.yml (Mazarini)

This PR was squashed before being merged into the master branch (closes #1007).

Discussion
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Add symfony 4.4 and 5.0 to .travis.yml

Add 2 tests with failures allowed :
For this 2 adds only :
- change memory_limit of PHP,
- add 'composer install' a  for 4.4 and 5.0 only
- change stability to dev
- change 'composer install' to 'composer update'
- suppress last (composer.json change)

Commits
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b698343 Add symfony 4.4 and 5.0 to .travis.yml

bocharsky-bw/symfony-demo,voronkovich/symfony-demo,symfony/symfony-demo,symfony/symfony-demo,TomasVotruba/symfony-demo,javiereguiluz/symfony-demo,symfony/symfony-demo,Codeception/symfony-demo,TomasVotruba/symfony-demo,javiereguiluz/symfony-demo,Codeception/symfony-demo,TomasVotruba/symfony-demo,voronkovich/symfony-demo,bocharsky-bw/symfony-demo,voronkovich/symfony-demo,javiereguiluz/symfony-demo,bocharsky-bw/symfony-demo,Codeception/symfony-demo