Skip non members

Hello,

You already know, this is patch about doesn't throw exception when json data has non class memebers.
I added a test about `SkipNonMembers`.
The test included `array` and `object`.
I made a wrapping method called `ReadSkip` at `JsonMapper` class.
It read json block using `JsonMapper.ReadValue()`.
Just skipping only.

Review please.