Fixed image building problem

[aorestr]

I found this problem while I was creating the Docker image:

Step 7/21 : RUN gem install gauntlt --no-rdoc --no-ri
 ---> Running in e9f499f67a38
!    The 'trollop' gem has been deprecated and has been replaced by 'optimist'.
!    See: https://rubygems.org/gems/optimist
!    And: https://github.com/ManageIQ/optimist
Successfully installed trollop-2.9.10
Successfully installed mini_portile2-2.4.0
Building native extensions.  This could take a while...
ERROR:  Error installing gauntlt:
	childprocess requires Ruby version >= 2.4.0.
Successfully installed nokogiri-1.10.10
Successfully installed rspec-support-3.10.0
Successfully installed diff-lcs-1.4.4
Successfully installed rspec-expectations-3.10.0
The command '/bin/sh -c gem install gauntlt --no-rdoc --no-ri' returned a non-zero code: 1
Makefile:4: recipe for target 'build' failed
make: *** [build] Error 1

I easily fixed just by upgrading the Ubuntu version from 16.04 to 18.04 (I tried to 20.04 but it seemed harder so I left it like this). libcurl was required to be upgraded to, and installing apt-utils avoid the message debconf: delaying package configuration, since apt-utils is not installed that appeared several times during the installation.

Fixes #8
Fixes #18

[kckndrgn]

In addition to the Ubuntu revision change from 16.04 to 18.04 I needed to update libcurl3 to libcurl4 in order to run the 'make build' command.