LoadError: cannot load such file -- rspec/core/rake_task

When I rake, I got this error.

AllenLins-MacBook-Pro:geoblacklight allenlin$ rake -t
Resolving dependencies...
You must `gem install bundler` and `bundle install` to run rake tasks
rake aborted!
LoadError: cannot load such file -- rspec/core/rake_task
/Users/allenlin/Documents/USpatial/geoblacklight/Rakefile:12:in `require'
/Users/allenlin/Documents/USpatial/geoblacklight/Rakefile:12:in `<top (required)>'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/rake_module.rb:28:in `load'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/rake_module.rb:28:in `load_rakefile'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/application.rb:689:in `raw_load_rakefile'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/application.rb:94:in `block in load_rakefile'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/application.rb:176:in `standard_exception_handling'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/application.rb:93:in `load_rakefile'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/application.rb:77:in `block in run'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/application.rb:176:in `standard_exception_handling'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/2.2.0/rake/application.rb:75:in `run'
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/rake-10.4.2/bin/rake:33:in `<top (required)>'
/Users/allenlin/.rbenv/versions/2.2.2/bin/rake:23:in `load'
/Users/allenlin/.rbenv/versions/2.2.2/bin/rake:23:in `<main>'

However, I've run the 'gem install bundler' and 'bundle install' the rspec/core/rake_task actually exists, shown by

AllenLins-MacBook-Pro:geoblacklight allenlin$ gem which rspec/core/rake_task
/Users/allenlin/.rbenv/versions/2.2.2/lib/ruby/gems/2.2.0/gems/rspec-core-3.0.4/lib/rspec/core/rake_task.rb

I am lost here. Thanks so much for any help on this! I attached the Gemfile:

source 'https://rubygems.org'

# Specify your gem's dependencies in geoblacklight.gemspec
gemspec

# If we don't specify 2.11.0 we'll end up with sprockets 2.12.0 in the main
# Gemfile.lock but since sass-rails gets generated (rails new) into the test app
# it'll want sprockets 2.11.0 and we'll have a conflict
gem 'sprockets', '2.11.0'

# If we don't specify 3.2.15 we'll end up with sass 3.3.2 in the main
# Gemfile.lock but since sass-rails gets generated (rails new) into the test app
# it'll want sass 3.2.0 and we'll have a conflict
gem 'sass', '~> 3.2.0'
gem 'bootstrap-sass', ">= 3.2"

group :test do
  # Peg simplecov to < 0.8 until this is resolved:
  # http://ift.tt/1ImdzSt
  gem 'simplecov', '~> 0.7.1', require: false
  gem 'coveralls', require: false
end