fixed prediacter methods so that empty string return false

[stebo]

I found a small bug in my last pull request which added the predicater methods: if you got an empty string like book.title = "" than book.title? will return TRUE - but should return FALSE!

The mistake was using !!value for all attributes, because in plain ruby

empty_string = ""
=> ""
!!empty_string
=> true

But Rails ActiveRecord does not simply use !!value - it differs between types and if the type is a string than it uses !value.blank? ... which is much better because of course if we check an object attribute with an emtpy string we want

book.title = ""
=> ""
book.title?
=> false

[ramontayag]

Yes, you're right - that's how AR does it. Thanks!

[ramontayag]

2.2.1 released