minor #118 Remove support for Symfony 3.4 (pamil)

This PR was merged into the 2.1-dev branch.

Discussion
----------

If you need Symfony 3.4 support, I'd recommend using `v2.0.*` releases, supporting two major Symfony versions is enough maintenance work 🎉 

Commits
-------

fcf957dc5a Remove support for Symfony 3.4

.travis.yml

@@ -7,7 +7,6 @@ php:
     - '7.4'
 
 env:
-    - SYMFONY_VERSION=3.4.*
     - SYMFONY_VERSION=4.4.*
     - SYMFONY_VERSION=5.0.*
 
@@ -34,8 +33,6 @@ install:
     - composer require --dev symfony/process:${SYMFONY_VERSION} --no-update --no-scripts --prefer-dist
     - composer require --dev symfony/yaml:${SYMFONY_VERSION} --no-update --no-scripts --prefer-dist
 
-    - if [ "$SYMFONY_VERSION" = "5.0.*" ]; then composer require --dev behat/behat:dev-master --no-update --no-scripts --prefer-dist; fi
-
     - composer update --prefer-dist
 
 script:

composer.json

@@ -13,9 +13,9 @@
     "require": {
         "php": "^7.1",
         "behat/behat": "^3.6.1",
-        "symfony/dependency-injection": "^3.4|^4.4|^5.0",
+        "symfony/dependency-injection": "^4.4|^5.0",
-        "symfony/http-kernel": "^3.4|^4.4|^5.0",
+        "symfony/http-kernel": "^4.4|^5.0",
-        "symfony/proxy-manager-bridge": "^3.4|^4.4|^5.0"
+        "symfony/proxy-manager-bridge": "^4.4|^5.0"
     },
     "require-dev": {
         "friends-of-behat/mink": "^1.7",
@@ -26,10 +26,10 @@
         "friends-of-behat/service-container-extension": "^1.0",
         "phpstan/phpstan-shim": "^0.11",
         "sylius-labs/coding-standard": "^3.0",
-        "symfony/browser-kit": "^3.4|^4.4|^5.0",
+        "symfony/browser-kit": "^4.4|^5.0",
-        "symfony/framework-bundle": "^3.4|^4.4|^5.0",
+        "symfony/framework-bundle": "^4.4|^5.0",
-        "symfony/process": "^3.4|^4.4|^5.0",
+        "symfony/process": "^4.4|^5.0",
-        "symfony/yaml": "^3.4|^4.4|^5.0"
+        "symfony/yaml": "^4.4|^5.0"
     },
     "conflict": {
         "symplify/package-builder": "^7.2",