Linux
sudo apt-get install libpq-dev POSTGRES_INCLUDE=/usr/include/postgresql sudo gem install postgres
OS X
POSTGRES_INCLUDE=/opt/local/include/postgresql82 sudo gem install postgres -- --with-pgsql-lib-dir=/opt/local/lib/postgresql82
sudo apt-get install libpq-dev POSTGRES_INCLUDE=/usr/include/postgresql sudo gem install postgres
POSTGRES_INCLUDE=/opt/local/include/postgresql82 sudo gem install postgres -- --with-pgsql-lib-dir=/opt/local/lib/postgresql82
