Update according to 0.3 of psr-18

Author: Nyholm

composer.json

@@ -17,7 +17,7 @@
     "require": {
         "php": "^7.0",
         "psr/http-message": "^1.0",
-        "psr/http-client": "^0.2",
+        "psr/http-client": "^0.3",
         "php-http/promise": "^1.0"
     },
     "require-dev": {

src/Exception.php

@@ -2,7 +2,7 @@
 
 namespace Http\Client;
 
-use Psr\Http\Client\ClientException as PsrClientException;
+use Psr\Http\Client\ClientExceptionInterface as PsrClientException;
 
 /**
  * Every HTTP Client related Exception must implement this interface.

src/Exception/NetworkException.php

@@ -2,7 +2,7 @@
 
 namespace Http\Client\Exception;
 
-use Psr\Http\Client\NetworkException as PsrNetworkException;
+use Psr\Http\Client\NetworkExceptionInterface as PsrNetworkException;
 
 /**
  * Thrown when the request cannot be completed because of network issues.

src/Exception/RequestException.php

@@ -3,7 +3,7 @@
 namespace Http\Client\Exception;
 
 use Psr\Http\Message\RequestInterface;
-use Psr\Http\Client\RequestException as PsrRequestException;
+use Psr\Http\Client\RequestExceptionInterface as PsrRequestException;
 
 /**
  * Exception for when a request failed, providing access to the failed request.