Discourage libevent on PHP 7

Author: cboden

src/Factory.php

@@ -7,12 +7,12 @@ class Factory
     public static function create()
     {
         // @codeCoverageIgnoreStart
-        if (function_exists('event_base_new')) {
-            return new LibEventLoop();
-        } elseif (class_exists('libev\EventLoop', false)) {
+        if (class_exists('libev\EventLoop', false)) {
             return new LibEvLoop;
         } elseif (class_exists('EventBase', false)) {
             return new ExtEventLoop;
+        } elseif (function_exists('event_base_new') && version_compare(PHP_VERSION, '7.0.0', '<')) {
+            return new LibEventLoop();
         }
 
         return new StreamSelectLoop();

src/LibEventLoop.php

@@ -31,6 +31,10 @@ class LibEventLoop implements LoopInterface
 
     public function __construct()
     {
+        if (version_compare(PHP_VERSION, '7.0.0') >= 0) {
+            trigger_error('The libevent extension has not yet been updated for PHP 7, it is recommended you use a different loop', E_USER_WARNING);
+        }
+
         $this->eventBase = event_base_new();
         $this->nextTickQueue = new NextTickQueue($this);
         $this->futureTickQueue = new FutureTickQueue($this);