To configure a Rails application in order to use SQLite3 please follow the following steps:
sudo apt-get install sqlite3 swig libsqlite3-ruby libsqlite3-dev sudo gem install sqlite3-ruby
Then create a Rails application as usual and update the environment.rb file in the following way
Rails::Initializer.run do |config|
config.gem 'sqlite3-ruby', :lib => "sqlite3"