Changes required in documentation

[prabhakar267]

While setting up the system for development, I found the following things missing or incorrect in the documentation.

setup_environment.md

• In Ubuntu system setup, postgresql-9.4 shows this error : Unable to locate package postgresql-9.4 in Ubuntu 14.04 LTS (solution: https://askubuntu.com/questions/633919/how-install-postgresql-9-4).

quickstart.md

• Before Step 2 (Run the bootstrap task), I had to install bundler by running the command gem install bundler followed by installing all the dependencies bundle install
  (Again for which I had to install a few gems like sqlite3 using apt-get install libsqlite3-dev and gem install sqlite3)

/cc @gdpelican

[gdpelican]

Would you be willing to submit a PR for these changes @prabhakar267 ?

[prabhakar267]

@gdpelican sure I will do it. There are a few steps missing regards the database setup as discussed with @robguthrie
I will do all the changes in one PR