Leetcode 57: Insert Interval 让代码更好读, 更容易测试.

阅读了几个博客, 决定写一个简易版本; 忙着做更多题, 没有时间多考虑优化代码, 所以, 就写一个试试运气. 

http://blog.csdn.net/kenden23/article/details/17264441

http://blog.csdn.net/worldwindjp/article/details/21612731

Two versions are compared in the following blog:

http://simpleandstupid.com/2014/10/29/insert-interval-leetcode-%E8%A7%A3%E9%A2%98%E7%AC%94%E8%AE%B0/

Julia worked on the code, and then, make code more abstract, readable and testable.
https://github.com/jianminchen/Leetcode_C-/blob/master/57InsertIntervals.cs