Added possibility to watch over multiple children nodes in sub query

[ailjushkin]

Now we are able to select nodes like this:

$.info[?(@.decl.code == 'code1')].values..value

So now @.decl.code can output upper object out of brackets in any level.

[ailjushkin]

I will check failed tests

[ailjushkin]

closing to restart travis build

[ailjushkin]

Fixed code to pass all tests

[joshbuddy]

Want to write a test case for this as well? Otherwise, seems okay!

[ailjushkin]

@joshbuddy ready to check :)

[ailjushkin]

@joshbuddy

explanation to let you understand why that test needs compact function.

1. I changed example object in tests
2. I added three books without price parameter - why not?
3. Then I found that this test failed. And it's failed because reference object created through the collect frunction. In the collect function, we are trying to get prices of books, node['price']. For my new three nodes without price parameters , node['price'] will return nil and output array will look like [1,2,3,nil,nil,nil].
4. Then look on jsonpath. It's searching for price parameter. Of course, It will never return my new three nodes without price parameter.
5. To make reference object look like it's output of jsonpath, I added compact function. It removes nil from the array and then the test could be passed.

Other tests were failed because of they are very depended on input data - fixed indexes.
Another test failed because it was comparing by price while filtering in jsonpath.
When jsonpath trying to evaluate @current_node['price'] < 10 on my nodes without price parameter, we get an error, becase @current_node['price'] is nil and nil < 10 not allowed operation. So I wrapped this "as is" eval with rescue.