Delete .travis.yml As We Switch To Azure Pipelines

Azure Pipelines have been made to work well enough for this project.  All other CI systems are to be disabled as mentioned dunder #308 

Delete the .travis.yml file now that it is not longer needed.  It can be recovered from git history if we ever wish to resurrect it.  

A separate action will need to be taken by someone with administrator access to the present https://travis-ci.org/debauchee/barrier project to unlink from the system there.

.travis.yml

@@ -1,34 +0,0 @@
-language: cpp
-
-matrix:
-  include:
-    - os: linux
-      sudo: false
-      dist: trusty
-      addons:
-        apt:
-          packages:
-            - libxtst-dev
-            - qtdeclarative5-dev
-            - libavahi-compat-libdnssd-dev
-      script: sh -x ./clean_build.sh
-
-    - os: osx
-      osx_image: xcode9
-      script:
-        - export COLUMNS=80
-        - curl -LO https://raw.githubusercontent.com/GiovanniBussi/macports-ci/master/macports-ci
-        - chmod +x ./macports-ci
-        - ./macports-ci install
-        - PATH="$PATH:/opt/local/bin"
-        - sudo port -N install qt5-qtbase openssl
-        - sh -x ./clean_build.sh
-
-    - os: osx
-      osx_image: xcode9
-      script:
-        - brew update
-        - brew install qt openssl
-        - sh -x ./clean_build.sh
-
-install: true