update cache-plugin based on 1.2.0 changelog

Author: alcohol

DependencyInjection/Configuration.php

@@ -369,7 +369,7 @@ private function addSharedPluginNodes(ArrayNodeDefinition $pluginNode, $disableA
                     ->arrayNode('config')
                         ->addDefaultsIfNotSet()
                         ->children()
-                            ->scalarNode('default_ttl')->defaultNull()->end()
+                            ->scalarNode('default_ttl')->defaultValue(0)->end()
                             ->scalarNode('respect_cache_headers')->defaultTrue()->end()
                         ->end()
                     ->end()

composer.json

@@ -20,7 +20,7 @@
         "php-http/client-implementation": "^1.0",
         "php-http/message-factory": "^1.0.2",
         "php-http/client-common": "^1.2",
-        "php-http/cache-plugin": "^1.0",
+        "php-http/cache-plugin": "^1.2",
         "php-http/logger-plugin": "^1.0",
         "php-http/stopwatch-plugin": "^1.0",
         "symfony/options-resolver": "^2.8 || ^3.0",