Remove copyright headers from code

Author: Lars-Magnus Skog

errors.js

@@ -1,9 +1,3 @@
-/* Copyright (c) 2012-2017 LevelUP contributors
- * See list at <https://github.com/rvagg/node-levelup#contributing>
- * MIT License
- * <https://github.com/rvagg/node-levelup/blob/master/LICENSE.md>
- */
-
 var createError = require('errno').create
 var LevelUPError = createError('LevelUPError')
 var NotFoundError = createError('NotFoundError', LevelUPError)