Update discovery version and dependencies

Author: sagikazarmark

composer.json

@@ -13,7 +13,7 @@
     ],
     "require": {
         "php": ">=5.5",
-        "php-http/discovery": "^0.7",
+        "php-http/discovery": "^0.8",
         "php-http/client-implementation": "^1.0",
         "php-http/message-factory": "^1.0",
         "php-http/plugins": "^1.0",
@@ -23,10 +23,14 @@
         "phpunit/phpunit": "^4.5",
         "php-http/guzzle6-adapter": "^1.0",
         "php-http/message": "^1.0",
+        "puli/composer-plugin": "1.0.0-beta9",
         "symfony/symfony": "^2.7|^3.0",
         "polishsymfonycommunity/symfony-mocker-container": "^1.0",
         "matthiasnoback/symfony-dependency-injection-test": "^0.7"
     },
+    "suggest": {
+        "puli/composer-plugin": "Used to set up Puli modules from composer packages"
+    },
     "autoload": {
         "psr-4": {
             "Http\\HttplugBundle\\": ""
@@ -41,6 +45,6 @@
             "dev-master": "1.0-dev"
         }
     },
-    "minimum-stability": "dev",
-    "prefer-stable": true
+    "prefer-stable": true,
+    "minimum-stability": "beta"
 }