cherry-picked the container-based travis config from 2.4

.travis.yml

@@ -8,12 +8,20 @@ env:
   - COVERALLS=true
   - COVERALLS=false
 
+sudo: false
+
+addons:
+  apt:
+    packages:
+    - unzip
+    - python3
+
 before_install:
-    - sudo apt-get -y update
-    - sudo apt-get -y install unzip python3
     - wget https://github.com/bioperl/bioperl-live/archive/bioperl-release-1-2-3.zip
     - unzip bioperl-release-1-2-3.zip
-    - sudo sed -i '1s/usr\/bin\/perl -w/usr\/bin\/env perl/' `which psql`
+    - echo -e '#!/bin/bash\n\nperl '`which psql`' "$@"' > psql
+    - chmod +x psql
+    - export PATH=$PWD:$PATH
     - ln -s /usr/share/perl5/PgCommon.pm modules/