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
Refactor quoting of identifiers and strings, with optional non-quoting of
identifiers in Postgres
Merge branch 'case-insensitive' of git://github.com/optilude/sequelize into optilude-case-insensitive
Merge branch 'optilude-case-insensitive'
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
Merge branch 'master' of github.com:sequelize/sequelize
Merge branch 'master' into milestones/2.0.0