Some gems apparently need to be coaxed by installing some packages on
Ubuntu prior to running them. Among the problematic gems, they
include:

* nokogiri
* starling
* typhoeus

For nokogiri:
sudo apt-get install libxml2-dev libxslt1-dev

For starling:
sudo apt-get install build-essential zlib1g-dev libssl-dev libreadline5-dev

For typhoeus:
sudo apt-get install libcurl4-gnutls-dev