Ao executar o bundle install a seguinte mensagem aparece: gem pg failed to build gem native extension

Olá pessoal iniciando os trabalhos no terceiro módulo na trilha ruby on rails ao executar o bundle instalme deparo com a seguinte mensagem de erro:

Users/betao/.rvm/rubies/ruby-2.1.2/bin/ruby extconf.rb
checking for pg_config... no
No pg_config... trying anyway. If building fails, please try again with
 --with-pg-config=/path/to/pg_config
checking for libpq-fe.h... no
Can't find the 'libpq-fe.h header
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
        --with-opt-dir
        --without-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=/Users/betao/.rvm/rubies/ruby-2.1.2/bin/ruby
        --with-pg
        --without-pg
        --with-pg-dir
        --without-pg-dir
        --with-pg-include
        --without-pg-include=${pg-dir}/include
        --with-pg-lib
        --without-pg-lib=${pg-dir}/lib
        --with-pg-config
        --without-pg-config
        --with-pg_config
        --without-pg_config
`

O que fiz? fui no gemset e comentei o a linha:

gem 'pg', group: :production

Bem acredito que se mais pra frente no curso precisar dela, eu instalo o postgree ($ brew install postgresql) e tento novamente executar o bundle.

Alguém mais passou por este problema? O que fizeram? desde já obrigado pela atenção.