Install all database components at once
Add commands for setting up database users in Postgres
Link the database.yml file instead of copying it

It is harder to ignore changes to the default database.yml.postgresql
file if the file is a link instead of a copy.
Update GnuLinux installation instructions for Ubuntu 14.04
Switch ruby-execjs for libv8-dev

libv8-dev is all that is needed and ruby-execjs included other things
that will be handled by bundler.
Fix a typo
Configure libv8 in the Gemfile instead of installing it separately
Merge pull request #38 from ferrous26/master

Update installation instructions for Ubuntu 14.04