Symfony 4 support

[FabienPapet]

Hello, While trying to install FOSElastica, I have this error.

Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Installation request for friendsofsymfony/elastica-bundle dev-master -> satisfiable by friendsofsymfony/elastica-bundle[dev-master].
    - friendsofsymfony/elastica-bundle dev-master requires symfony/framework-bundle ^2.7 || ^3.1 -> satisfiable by symfony/framework-bundle[2.7.x-dev, 2.8.x-dev, 3.1.x-dev, 3.2.x-dev, 3.3.x-dev, 3.4.x-dev, v2.7.0, v2.7.0-BETA1, v2.7.0-BETA2, v2.7.1, v2.7.10, v2.7.11,
v2.7.12, v2.7.13, v2.7.14, v2.7.15, v2.7.16, v2.7.17, v2.7.18, v2.7.19, v2.7.2, v2.7.20, v2.7.21, v2.7.22, v2.7.23, v2.7.24, v2.7.25, v2.7.26, v2.7.27, v2.7.28, v2.7.29, v2.7.3, v2.7.30, v2.7.31, v2.7.32, v2.7.33, v2.7.34, v2.7.35, v2.7.36, v2.7.37, v2.7.38, v2.7.4, v
2.7.5, v2.7.6, v2.7.7, v2.7.8, v2.7.9, v2.8.0, v2.8.0-BETA1, v2.8.1, v2.8.10, v2.8.11, v2.8.12, v2.8.13, v2.8.14, v2.8.15, v2.8.16, v2.8.17, v2.8.18, v2.8.19, v2.8.2, v2.8.20, v2.8.21, v2.8.22, v2.8.23, v2.8.24, v2.8.25, v2.8.26, v2.8.27, v2.8.28, v2.8.29, v2.8.3, v2.
8.30, v2.8.31, v2.8.4, v2.8.5, v2.8.6, v2.8.7, v2.8.8, v2.8.9, v3.1.0, v3.1.0-BETA1, v3.1.0-RC1, v3.1.1, v3.1.10, v3.1.2, v3.1.3, v3.1.4, v3.1.5, v3.1.6, v3.1.7, v3.1.8, v3.1.9, v3.2.0, v3.2.0-BETA1, v3.2.0-RC1, v3.2.0-RC2, v3.2.1, v3.2.10, v3.2.11, v3.2.12, v3.2.13,
v3.2.14, v3.2.2, v3.2.3, v3.2.4, v3.2.5, v3.2.6, v3.2.7, v3.2.8, v3.2.9, v3.3.0, v3.3.0-BETA1, v3.3.0-RC1, v3.3.1, v3.3.10, v3.3.11, v3.3.12, v3.3.13, v3.3.2, v3.3.3, v3.3.4, v3.3.5, v3.3.6, v3.3.7, v3.3.8, v3.3.9, v3.4.0, v3.4.0-BETA1, v3.4.0-BETA2, v3.4.0-BETA3, v3.
4.0-BETA4, v3.4.0-RC1, v3.4.0-RC2] but these conflict with your requirements or minimum-stability.

Is Symfony4 compatible with FosElastica ?

[devgogo]

Call @XWB

[dkarlovi]

See #1302

[makasim]

Closing because there are PRs addressing the issue https://github.com/FriendsOfSymfony/FOSElasticaBundle/issues/1316, https://github.com/FriendsOfSymfony/FOSElasticaBundle/pull/1331