Installing Merb, DataMapper and Postgres on Ubuntu

This isn't particularly difficult, but if you're not familiar with Postgres on Ubuntu it could take you ten minutes to work it out:

$ sudo apt-get install postgresql-8.2 postgresql-server-dev-8.2 -y
$ sudo apt-get install libsqlite3-dev -y
$ sudo gem install merb do_postgres

The merb gem depends on the do_sqlite3 DataMapper database driver, so we need the libsqlite3-dev package in order to compile it. You can remove it afterwards if you like.