Fixed documentation

Author: Mitchel Verschoof

doc/result_pager.md

@@ -11,7 +11,7 @@ $client = new Github\Client();
 $organizationApi = $client->api('organization');
 
 $paginator = new Github\ResultPager( $client );
-$result    = $paginator->fetchAll( $organizationApi, 'repositories', 'github );
+$result    = $paginator->fetchAll( $organizationApi, 'repositories', 'github' );
 ```
 
 Get the first page
@@ -21,7 +21,7 @@ $client = new Github\Client();
 $organizationApi = $client->api('organization');
 
 $paginator = new Github\ResultPager( $client );
-$result    = $paginator->fetch( $organizationApi, 'repositories', 'github );
+$result    = $paginator->fetch( $organizationApi, 'repositories', 'github' );
 ```
 Check for a next page:
 ```php
@@ -35,7 +35,7 @@ $paginator->fetchNext();
 
 Check for pervious page:
 ```php
-$paginator->getPrevious();
+$paginator->hasPrevious();
 ```
 
 Get prevrious page: