issue #10

In Windows, if there are a lot of files in the task, the command line will be too long. Thus error 'The command line is too long' will occur.

This problem is fixed by limiting the length of each command.
issue #10 only check Windows

Currently, only check Windows platform (XP or later)
issue #10, extract common code logic
Merge pull request #12 from ganxiyun/master

issue #10