Can't install because 'sqlite3' not found

[dkellygb]

Just wanted to evaluate Fat Free CRM. Couldn't install because it failed with:
`Gem files will remain installed in /var/lib/gems/2.5.0/gems/sqlite3-1.3.13 for inspection.
Results logged to /var/lib/gems/2.5.0/extensions/x86_64-linux/2.5.0/sqlite3-1.3.13/gem_make.out

An error occurred while installing sqlite3 (1.3.13), and Bundler cannot continue.
Make sure that gem install sqlite3 -v '1.3.13' --source 'https://rubygems.org/' succeeds before bundling.

In Gemfile:
acts_as_fu was resolved to 0.0.9, which depends on
sqlite3
`
Also, failed because

current directory: /var/lib/gems/2.5.0/gems/pg-0.21.0/ext /usr/bin/ruby2.5 -I /usr/local/lib/site_ruby/2.5.0 -r ./siteconf20190311-6307-e3t6ep.rb extconf.rb checking for pg_config... yes Using config values from /usr/bin/pg_config You need to install postgresql-server-dev-X.Y for building a server-side extension or libpq-dev for building a client-side application. You need to install postgresql-server-dev-X.Y for building a server-side extension or libpq-dev for building a client-side application. checking for libpq-fe.h... no Can't find the 'libpq-fe.h header
This is on Ubuntu 18.04 server.

Installed sqlite3 and postgresql-server-dev-10 from apt. This seemed to fix the problems but the install guide needs to be updated.