改进对反射的描述

原句中`所谓反射就是动态运行时的状态。`,去掉形容词就是说`反射就是状态`?

按照The Laws of Reflection中的解释: `Reflection in computing is the ability of a program to examine its own structure, particularly through types;`

可以看出反射是程序的一种能力。FYI.
Merge pull request #302 from mikulely/patch-5

改进对反射的描述