Revert "Switched Map to fromJS in order to convert the whole js object (also nested data structures) to immutable (#2619)" (#2687)
Revert "Switched Map to fromJS in order to convert the whole js object (also nested data structures) to immutable (#2619)" (#2687)

This reverts commit b8c372df93ac94b3d0449e0c496cdf8bec9af0fc.
isubastiCadmus/slate,ianstormtaylor/slate,ianstormtaylor/slate