Heroku pg eror

gistfile1.txt

root@spandan:/opt/Rails-project-For-Student-Forum# heroku run rake db:migrate
Running rake db:migrate attached to terminal... up, run.5
rake aborted!
Please install the postgresql adapter: `gem install activerecord-postgresql-adapter` (can't activate pg (~> 0.11, runtime), already activated pg-0.10.0. Make sure all dependencies are added to Gemfile.)

Tasks: TOP => db:migrate => db:load_config
(See full trace by running task with --trace)
root@spandan:/opt/Rails-project-For-Student-Forum# 

How to Solve this error ?
Please help

My Gitfile

GNU nano 2.2.6 File: Gemfile

source 'http://rubygems.org'

gem 'rails', '3.1.0'

Bundle edge Rails instead:

gem 'rails', :git => 'git://github.com/rails/rails.git'

gem "heroku", "~> 2.8.0"
gem 'json'

gem 'thin'

gem 'hassle'

group :development do
gem 'rspec-rails', '2.6.1'
gem 'mysql2'
end

group :test do
gem 'rspec', '2.6.0'
gem 'webrat', '0.7.1'
gem 'spork', '0.8.4'
gem 'factory_girl_rails', '1.0'
end

group :production do

gem 'therubyracer-heroku', '0.8.1.pre3'

gem "pg", "~> 0.11.0"

end