Revert "Add missing logger dependency to fix bundle exec rake release"

This reverts commit 3c6aa06.

Author: ArturT

knapsack_pro.gemspec

@@ -27,7 +27,6 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.add_dependency 'rake', '>= 0'
-  spec.add_dependency 'logger'
 
   spec.add_development_dependency 'bundler', '>= 1.6'
   spec.add_development_dependency 'cucumber', '>= 0'