Updates in store are not tracked when putting already proxified objects in store

[andykog]

Only applies to es6 version of remx.
When reusing some object to define store state it's not being proxified more then once, hence accessing&modification properties inside it are not tracked.

The test case (currently skipped) is here: https://github.com/wix/remx/blob/master/src/integrationTests/EdgeCases.test.js#L98-L123