[composer] Replace self.version with ~2.4

version 2.4.* is LTS as should be the minimum required version

Author: Maks3w

composer.json

@@ -14,16 +14,16 @@
     },
     "require": {
         "php": ">=5.3.23",
-        "zendframework/zend-stdlib": "self.version"
+        "zendframework/zend-stdlib": "~2.4"
     },
     "require-dev": {
-        "zendframework/zend-db": "self.version",
-        "zendframework/zend-crypt": "self.version",
-        "zendframework/zend-http": "self.version",
-        "zendframework/zend-ldap": "self.version",
-        "zendframework/zend-session": "self.version",
-        "zendframework/zend-validator": "self.version",
-        "zendframework/zend-uri": "self.version",
+        "zendframework/zend-db": "~2.4",
+        "zendframework/zend-crypt": "~2.4",
+        "zendframework/zend-http": "~2.4",
+        "zendframework/zend-ldap": "~2.4",
+        "zendframework/zend-session": "~2.4",
+        "zendframework/zend-validator": "~2.4",
+        "zendframework/zend-uri": "~2.4",
         "fabpot/php-cs-fixer": "1.7.*",
         "satooshi/php-coveralls": "dev-master",
         "phpunit/PHPUnit": "~4.0"