Travis uses rvm, use it to install ruby 2.3.0

.travis.yml

@@ -100,9 +100,7 @@ matrix:
       env: SWIGLANG=ruby
     - compiler: gcc
       os: linux
-      env: SWIGLANG=ruby VER=2.3
-      sudo: required
-      dist: trusty
+      env: SWIGLANG=ruby VER=2.3.0
     - compiler: gcc
       os: linux
       env: SWIGLANG=scilab

Tools/travis-linux-install.sh

@@ -93,12 +93,7 @@ case "$SWIGLANG" in
 		;;
 	"ruby")
 		if [[ "$VER" ]]; then
-			sudo apt-get -qq install python-software-properties
-			sudo add-apt-repository -y ppa:brightbox/ruby-ng
-			sudo apt-get -qq update
-			sudo apt-get -qq install ruby2.3 ruby2.3-dev
-#			sudo gem pristine --all # Results in: You don't have write permissions for the /var/lib/gems/2.3.0 directory
-			WITHLANG=$SWIGLANG=$SWIGLANG$VER
+			rvm install $VER
 		fi
 		;;
 	"scilab")