The project runs on a specific version of Ruby, specified in .ruby-version. You can check your Ruby version by running:
ruby -v
If you need to install a newer version of Ruby, we recommend using rbenv and ruby-build.
You can use Homebrew to install Postgres: brew install postgres
There's good information about how to use it at: brew info postgres
And you can start a Postgres server with postgres -D /usr/local/var/postgres
On El Capitan, Puma expects headers for a version of OpenSSL that is no longer included in the OS. This will cause bundle install to fail. See puma/puma#718 for more information.
You can workaround like this:
bundle config build.puma --with-opt-include=/usr/local/opt/openssl/include
bundle install
On a Debian-like OS you may have to remove this line from the config of the development database (config/database.yml)
host: localhost
For an explanation, see this Stackoverflow discussion.
On Gentoo, you may need to ensure that your username exists as a Postgres user.