Your Ruby version is 2.0.0, but your Gemfile specified 2.1.0

In the top-level directory of your project, create a file named .ruby-version containing (wait for it...)

2.1.0

That apparently is the cross-{rbenv,rvm} way of spec'ing the version now.

Run

gem install bundler

or

gem update bundler 

which may fix your problem.

For all new installed versions of Ruby you should update or install a new bundler.