The AddHost plugin should take care of the base path

With the following PHP code example:

```php
$httpClient = new HttpMethodsClient(
    new PluginClient(HttpClientDiscovery::find(), [
        new AddHostPlugin(UriFactoryDiscovery::find()->createUri('https://logs.domain.com/api')),
        new ErrorPlugin(),
    ]),
    MessageFactoryDiscovery::find()
);
$httpClient->get('/users');
```

The https://logs.domain.com/users URL will be called instead of /api/users.

The base path should be kept on this plugin.

Author: soullivaneuh

CHANGELOG.md

@@ -11,7 +11,7 @@
 
 - Fix Emulated Trait to use Http based promise which respect the HttpAsyncClient interface
 - RedirectPlugin: use the full URL instead of the URI to properly keep track of redirects
-
+- AddHostPlugin now keeps the base path of the URI
 
 ## 1.2.1 - 2016-07-26
 

spec/Plugin/AddHostPluginSpec.php

@@ -37,14 +37,17 @@ function it_adds_domain(
         $host->getScheme()->shouldBeCalled()->willReturn('http://');
         $host->getHost()->shouldBeCalled()->willReturn('example.com');
         $host->getPort()->shouldBeCalled()->willReturn(8000);
+        $host->getPath()->shouldBeCalled()->willReturn('/api');
 
         $request->getUri()->shouldBeCalled()->willReturn($uri);
         $request->withUri($uri)->shouldBeCalled()->willReturn($request);
 
         $uri->withScheme('http://')->shouldBeCalled()->willReturn($uri);
         $uri->withHost('example.com')->shouldBeCalled()->willReturn($uri);
         $uri->withPort(8000)->shouldBeCalled()->willReturn($uri);
+        $uri->withPath('/api/users')->shouldBeCalled()->willReturn($uri);
         $uri->getHost()->shouldBeCalled()->willReturn('');
+        $uri->getPath()->shouldBeCalled()->willReturn('/users');
 
         $this->beConstructedWith($host);
         $this->handleRequest($request, function () {}, function () {});
@@ -58,13 +61,16 @@ function it_replaces_domain(
         $host->getScheme()->shouldBeCalled()->willReturn('http://');
         $host->getHost()->shouldBeCalled()->willReturn('example.com');
         $host->getPort()->shouldBeCalled()->willReturn(8000);
+        $host->getPath()->shouldBeCalled()->willReturn('/api');
 
         $request->getUri()->shouldBeCalled()->willReturn($uri);
         $request->withUri($uri)->shouldBeCalled()->willReturn($request);
 
         $uri->withScheme('http://')->shouldBeCalled()->willReturn($uri);
         $uri->withHost('example.com')->shouldBeCalled()->willReturn($uri);
         $uri->withPort(8000)->shouldBeCalled()->willReturn($uri);
+        $uri->withPath('/api/users')->shouldBeCalled()->willReturn($uri);
+        $uri->getPath()->shouldBeCalled()->willReturn('/users');
 
         $this->beConstructedWith($host, ['replace' => true]);
         $this->handleRequest($request, function () {}, function () {});

src/Plugin/AddHostPlugin.php

@@ -56,6 +56,7 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
                 ->withHost($this->host->getHost())
                 ->withScheme($this->host->getScheme())
                 ->withPort($this->host->getPort())
+                ->withPath($this->host->getPath().$request->getUri()->getPath())
             ;
 
             $request = $request->withUri($uri);