adopt lot-parser v0.3.1

Improved program structure et cetera please see lot-parser for details.
Maybe I need a more comprehensive automated testing process.
change name to OL.cn

dedicated to problem database
we should split yan.ac into several small projects
devDependencies => dependencies
IOL 2003 p4 rewritten
rethink about <p> and text nodes
remove unnecessary + misleading comments
明日复明日……明日再重构。