Fixed rakefile
Register assignment[assignment_ruby_001]
Register assignment[assignment_ruby_002]
Register assignment[assignment_ruby_003]
Git fetch branches when executing rake solve
Improve Gemfile
Revert "Improve Gemfile"

This reverts commit 178c28d3fd7bd67b6109ba8d0e4a8ca4cbfa23f2.
Fixed Rakefile for sending pull_request
Merge branch 'master' into answer_assignment_ruby_001_huyu