Add support for bind variables

[fehays]

Issue #23

Bind variables

List<String> listOfNames = new List<String> {'Acme', 'Acme 2'};
    Q query =		
        new Q(Account.SObjectType)
            .add(Q.condition('Name').isIn(Q.bindVar(':listOfNames')))

System.debug(query.build());
// SELECT Id FROM Account WHERE Name IN :listOfNames