Improved compiling instructions

.travis.yml

@@ -1,23 +1,14 @@
 language: cpp
-dist: xenial
+dist: bionic
 matrix:
   include:
-  - #dist: xenial
-    compiler: g++
-    os: linux
-    sudo: required
-  - dist: bionic
+  - #dist: bionic
     compiler: g++
     os: linux
     sudo: required
 
 before_script: |
-    if [[ "$TRAVIS_DIST" == "xenial" ]]; then
-        sudo apt-get install git python3-pip
-        git clone https://github.com/SCons/scons.git
-    else
-        sudo apt-get install scons git python3-ruamel.yaml python3-yaml
-    fi
+    sudo apt-get install scons git python3-ruamel.yaml python3-yaml
     sudo apt-get install build-essential libgtkmm-3.0-dev g++ gfortran python libboost-dev cython python-dev python-numpy python-numpy-dev python-setuptools python3 python3-dev python3-setuptools python3-numpy cython3 python3-matplotlib
     sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 1
     git clone https://github.com/Cantera/cantera.git
@@ -29,16 +20,6 @@ env:
   global:
   - ASALI_OS='-DASALI_ON_WINDOW=0'
 script: |
-    if [[ "$TRAVIS_DIST" == "xenial" ]]; then
-        cd scons
-        python bootstrap.py build/scons
-        cd build/scons/
-        sudo python setup.py install
-        cd ..
-        cd ..
-        cd ..
-        pip3 install ruamel.yaml
-    fi
     cd cantera
     scons build system_sundials=n
     sudo scons install