Problems with empty objects on same level

[narcoticfresh]

After #28 and #30 we discovered another wrong behavior with empty objects in the path of operations..

-> I opened PR #32 to demonstrate the wrong behavior..

As it seems, it stems from the fact that json_decode($value, true) is also done in raphaelstolt/php-jsonpointer - thus objects are changed to arrays after performing the operation.

I'm not really sure how to proceed at that point.. I don't know where this lib (raphaelstolt/php-jsonpointer) is also used..

I tried to work around the issue by just taking the appropiate array member from whatever I get from php-jsonpointer, but that again makes problems with tests like this: https://github.com/raphaelstolt/php-jsonpatch/blob/master/tests/unit/Rs/Json/Patch/Operations/AddTest.php#L197

Can the same type of fix i did in this library (json_encode()ing to object) also be easily done in php-jsonpointer?

[narcoticfresh]

@raphaelstolt the new PR is #34, please see additional explanation there.. thanks