Add function noStandalone to disable --standalone

This implementation keeps backwards-compability by adding `--standalone`
in `run()` per default but not adding it per default in `execute()`.

It still can be set explicitely with `standalone()`, resulting in
`execute()` passing `--standalone`.

Additionally it can be disabled explicitely with `noStandalone()`,
resulting in `run()` not passing `--standalone`.

Fixes: #31

Signed-off-by: Jonas <jonas@freesources.org>

src/Pandoc.php

@@ -19,6 +19,8 @@ class Pandoc
 
     protected $input;
 
+    protected $standalone = true;
+
     protected $inputFile;
 
     protected $from;
@@ -127,6 +129,14 @@ public function tocDepth($value)
     public function standalone()
     {
         $this->option('standalone');
+        $this->standalone = true;
+
+        return $this;
+    }
+
+    public function noStandalone()
+    {
+        $this->standalone = false;
 
         return $this;
     }
@@ -197,10 +207,13 @@ public function execute(array $parameters = [])
     public function run()
     {
         $parameters = [
-            '--standalone',
             '--sandbox',
         ];
 
+        if ($this->standalone) {
+            array_push($parameters, '--standalone');
+        }
+
         if ($this->inputFile) {
             array_push($parameters, $this->inputFile);
         }