Added option to start with no handle by setting default_position to :none
Moved default_position logic to the dsl.

Closes #106

LGTM given by: @esposito

Squashed commit of the following:

commit dbf59c97389a37e3f58db2ac94b9e17f1e5f0b57
    moved slider default_position middle to dsl
commit 195699a6fd2a3eb95346c33d2c9b9e6282cbb5b8
    added option to start with no handle by setting default_position below the min value
allow only :all, :none, :paged and :bulk for question#show_values
Added show_values: :print option to question. Added show_values_in_mode? method to question
Made all view use the new show_values_in_mode? method. Fixed paged/checkbox that was showing when the value was :print.
Fixed and cleaned up _item_question_number_spec