Add evince to base Ubuntu container

Added evince to base Ubuntu 18.04 LTS container. User requires remote,
X11-forwarded PDF viewer on Expanse. However, current system library
support for CentOS 8 is not compatible with some exiting pre-compiled
binaries from PDF view projects like xpdf. This is a quick and dirty
fix/test to see if we can meet the user's requirement via a Singularity
container for the time being. Long-term, however, recommend removing
evince from this base container, unless absolutely necessary.

README.md

@@ -33,9 +33,7 @@ singularity pull shub://mkandes/naked-singularity:ubuntu-18.04
    
 ## Status
 
-The naked-singularity project is currently undergoing a major 
-restructuring of the repository. Significant changes over the next few 
-weeks should be expected.
+A work in progress. 
 
 ## Contribute
 
@@ -53,8 +51,8 @@ University of California, San Diego
 
 ## Version
 
-1.2.3
+1.2.4
 
 ## Last Updated
 
-Thursday, December 31st, 2020
+Tuesday, January 12th, 2021

definition-files/ubuntu/Singularity.ubuntu-18.04

@@ -11,7 +11,7 @@ OSVersion: bionic
     AUTHOR_NAME Marty Kandes
     AUTHOR_EMAIL mkandes@sdsc.edu
 
-    LAST_UPDATED 20200809
+    LAST_UPDATED 20210112
 
 %setup
 
@@ -76,6 +76,7 @@ OSVersion: bionic
     apt-get -y install automake
     apt-get -y install build-essential
     apt-get -y install cmake
+    apt-get -y install evince
     apt-get -y install expect
     apt-get -y install gfortran
     apt-get -y install libtool