add active_record_40 to Rakefile :spec task
Test against Rails edge
Test against sinatra 1.4, move sinatra -> sinatra_13
change #page_entries_info to use model name when collection is empty
use database_cleaner ~> 1.0.1 to avoid travis build errors

See bmabey/database_cleaner issue#224
limit to require activerecord 3.2.x for sinatra
fix build error in spec with sinatra

The error was 'NameError: uninitialized constant Kaminari::ActionViewExtension'.