Eu precisei instalar o MongoDB FDW para Postgresql no Travis CI e funcionou para mim. Assume a versão PG v9.3.
# in travis.yml
before_script:
- script/install_fdw
# script/install_fdw
#!/bin/sh
sudo apt-get install postgresql-server-dev-9.3
git clone https://github.com/citusdata/mongo_fdw
cd mongo_fdw/
PATH=/usr/lib/postgresql/9.3/bin/:$PATH make
sudo PATH=/usr/lib/postgresql/9.3/bin/:$PATH make install