This PR was merged into the master branch.

Discussion
----------

Updated to Symfony 3.1.5

Full composer update log:

```
  - Removing twig/twig (v1.25.0)
  - Installing twig/twig (v1.26.1)

  - Removing symfony/symfony (v3.1.4)
  - Installing symfony/symfony (v3.1.5)

  - Removing psr/log (1.0.0)
  - Installing psr/log (1.0.1)

  - Removing doctrine/dbal (v2.5.4)
  - Installing doctrine/dbal (v2.5.5)

  - Removing doctrine/orm (v2.5.4)
  - Installing doctrine/orm (v2.5.5)

  - Removing sensiolabs/security-checker (v3.0.2)
  - Installing sensiolabs/security-checker (v4.0.0)

  - Removing sensio/distribution-bundle (v5.0.9)
  - Installing sensio/distribution-bundle (v5.0.13)

  - Removing twig/extensions (v1.3.0)
  - Installing twig/extensions (v1.4.0)

  - Removing symfony/phpunit-bridge (v3.1.4)
  - Installing symfony/phpunit-bridge (v3.1.5)

  - Removing phpdocumentor/reflection-docblock (3.1.0)
  - Installing phpdocumentor/reflection-docblock (3.1.1)
```

Commits
-------

52e6824 Updated to Symfony 3.1.5