Added check for $this->eof() to buffer read

BufferStream::read() now checks $this->eof() and returns false if true.
implements #142 (one part of it)

src/CSVelte/IO/BufferStream.php

@@ -123,12 +123,12 @@ public function isReadable()
      */
     public function read($chars)
     {
-        if ($this->buffer === '') {
-            return false;
+        if (!$this->eof()) {
+            $data = substr($this->buffer, 0, $chars);
+            $this->buffer = substr($this->buffer, $chars);
+            return $data;
         }
-        $data = substr($this->buffer, 0, $chars);
-        $this->buffer = substr($this->buffer, $chars);
-        return $data;
+        return false;
     }
 
     /**