Fix belongsTo where params

Usually when adding to a `foobar.getBla()` a where param
like `foobar.getBla({where: {x: "y"}})` it should extend
the existing where param (`"id": id`) with the additional
where param.
This didn't work for belongsTo associations until now.
Add else case according to @janmeier's comment
Empty commit in order for travis to build again
Merge branch 'fix-belongs-to-where-params' of github.com:mweibel/sequelize into fix-belongs-to-where-params
Merge pull request #658 from mweibel/fix-belongs-to-where-params

Fix belongsTo where params
Update changelog