错误：
rake aborted!
Gem::LoadError: You have already activated rake 10.3.2, but your Gemfile requires rake 10.1.1. Prepending `bundle exec` to your command may solve this.
解决：
bundle exec rake db:migrate
bundle update
错误：
rake aborted!
Gem::LoadError: You have already activated rake 10.3.2, but your Gemfile requires rake 10.1.1. Prepending `bundle exec` to your command may solve this.
解决：
bundle exec rake db:migrate
bundle update