Don't report exception to Airbrake if simply missing some answer values

Closes #107

LGTM given by: @esposito

Squashed commit of the following:

commit 233b1504549019540b2a7e0cfe2d97510d497dd6
Author: Marten Veldthuis <marten@veldthuis.com>
Date:   Tue Nov 11 15:55:57 2014 +0100

    Please rubocop

commit 8e00480d639afd03d5f50ca323ca680e11e2cf2a
Author: Marten Veldthuis <marten@veldthuis.com>
Date:   Tue Nov 11 15:43:14 2014 +0100

    Raise specific exception, catch and set blank score

commit d10fc1210043e24ec5acb876848ae7154e6fabc1
Author: Marten Veldthuis <marten@veldthuis.com>
Date:   Tue Nov 11 14:36:40 2014 +0100

    Add questionnaire arg to ScoreCalculator
Fix regular values sorting
Sort unknown regular value keys to the end of the outcomecalculation regular values
cleanup hound config
validate score labels
don't report errors for score calculations returning nil
Fix unknown fields check for check_boxes
Dont run group_minimum validation when all items in group are hidden
Fix for completion not being a hash {value: {}}
Fix for nil result for score outcome
Fix calculation of group visible count
Add tests that check both min and max
Add test for saving questions showed by a flag
Move slider customization to file in app/assets
fix rubocop warning
Merge branch 'rel_201411'
Remove dumb ignore file (hello marten from 2011, wtf were you thinking), fix missing stylesheet
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.