make Ruby 1.9 to be default

1. sudo apt-get update
2. sudo apt-get install ruby1.9.1 ruby1.9.1-dev rubygems1.9.1 irb1.9.1 ri1.9.1 rdoc1.9.1 build-essential libopenssl-ruby1.9.1 libssl-dev zlib1g-dev
3. sudo update-alternatives --install /usr/bin/ruby ruby /usr/bin/ruby1.9.1 400 --slave /usr/share/man/man1/ruby.1.gz ruby.1.gz /usr/share/man/man1/ruby1.9.1.1.gz --slave /usr/bin/ri ri /usr/bin/ri1.9.1 --slave   /usr/bin/irb irb /usr/bin/irb1.9.1 --slave   /usr/bin/rdoc rdoc /usr/bin/rdoc1.9.1
4. sudo update-alternatives --config ruby (choose 1st variant /usr/bin/ruby1.9.1)
5. sudo update-alternatives --config gem (choose last variant with /usr/bin/gem1.9.1)

If you try 'ruby --version' will have the ruby1.9.1 version