Fix test to use new Select func

The current test code uses the old gorp Select func, as opposed to the new Select func (which returns multiple values, the first of which is the data, instead of writing into one of the params).

Thus running `go test` with go devel (built Mon Apr 15) yields a compile error:
`
$ go test
# gorp_test
./gorp_test.go:202: multiple-value dbmap.Select() in single-value context
./gorp_test.go:860: multiple-value dbmap.Select() in single-value context
FAIL	gorp [build failed]
`

After fixing the compile error, the tests fail at runtime for problems related to the same change.