ensure unique file names are returned (#1239)

* ensure unique file names are returned 

// glob() can return the same file multiple times
        // This will cause the migration to fail with a 
        // false assumption of duplicate migrations
        // http://php.net/manual/en/function.glob.php#110340

* fix spacing issue

src/Phinx/Migration/Manager.php

@@ -746,6 +746,11 @@ protected function getMigrationFiles()
                 Util::glob($path . DIRECTORY_SEPARATOR . '*.php')
             );
         }
+        // glob() can return the same file multiple times
+        // This will cause the migration to fail with a
+        // false assumption of duplicate migrations
+        // http://php.net/manual/en/function.glob.php#110340
+        $files = array_unique($files);
 
         return $files;
     }
@@ -838,6 +843,11 @@ protected function getSeedFiles()
                 Util::glob($path . DIRECTORY_SEPARATOR . '*.php')
             );
         }
+        // glob() can return the same file multiple times
+        // This will cause the migration to fail with a
+        // false assumption of duplicate migrations
+        // http://php.net/manual/en/function.glob.php#110340
+        $files = array_unique($files);
 
         return $files;
     }