Rename "dropTable" to "drop" in permalinks migration.

Fixes issues with uninstalling or refreshing plugin.

Fixes #37

updates/create_permalinks_table.php

@@ -29,7 +29,7 @@ public function up()
     public function down()
     {
         if (Schema::hasTable('abweb_imageresize_permalinks') === true) {
-            Schema::dropTable('abweb_imageresize_permalinks');
+            Schema::drop('abweb_imageresize_permalinks');
         }
     }
 }