bug #199 Revert SF 3.4 constraints (ro0NL)

This PR was squashed before being merged into the 3.1-dev branch (closes #199).

Discussion
----------

Revert SF 3.4 constraints

See #198

Just a quick PR to see what tests do, but i believe this was forgotten as we reverted special 3.4 features, exactly for BC.

Commits
-------

9572210 Revert SF 3.4 constraints

Author: stof

composer.json

@@ -18,15 +18,15 @@
     "require": {
         "php": ">=7.0.0",
         "swiftmailer/swiftmailer": "^6.0.1",
-        "symfony/dependency-injection": "~2.7|~3.4|~4.0",
-        "symfony/http-kernel": "~2.7|~3.0|~4.0",
-        "symfony/config": "~2.8|~3.0|~4.0"
+        "symfony/dependency-injection": "~2.7|~3.3|~4.0",
+        "symfony/http-kernel": "~2.7|~3.3|~4.0",
+        "symfony/config": "~2.8|~3.3|~4.0"
     },
     "require-dev": {
-        "symfony/console": "~2.7|~3.4|~4.0",
-        "symfony/framework-bundle": "~2.7|~3.0|~4.0",
+        "symfony/console": "~2.7|~3.3|~4.0",
+        "symfony/framework-bundle": "~2.7|~3.3|~4.0",
         "symfony/phpunit-bridge": "~3.3|~4.0",
-        "symfony/yaml": "~2.7|~3.0|~4.0"
+        "symfony/yaml": "~2.7|~3.3|~4.0"
     },
     "suggest": {
         "psr/log": "Allows logging"