log bind variables after they were type casted.

The log output used to be confusing in situation where type casting has
"unexpected" effects. For example when finding records with a `String`.

BEFORE:

irb(main):002:0> Event.find("im-no-integer")
D, [2013-11-09T11:10:28.998857 #1706] DEBUG -- :   Event Load (4.5ms)  SELECT "events".* FROM "events" WHERE "events"."id" = $1 LIMIT 1  [["id", "im-no-integer"]]

AFTER:

irb(main):002:0> Event.find("im-no-integer")
D, [2013-11-09T11:10:28.998857 #1706] DEBUG -- :   Event Load (4.5ms)  SELECT "events".* FROM "events" WHERE "events"."id" = $1 LIMIT 1  [["id", 0]]