Removed integration with Travis-CO

.travis.yml

-matrix:
-  include:
-    # Job 1) Run analyzer
-    - os: linux
-      env:
-        - SHARD=Analyze
-      sudo: false
-      addons:
-        apt:
-          # Flutter depends on /usr/lib/x86_64-linux-gnu/libstdc++.so.6 version GLIBCXX_3.4.18
-          sources:
-            - ubuntu-toolchain-r-test # if we don't specify this, the libstdc++6 we get is the wrong version
-          packages:
-            - libstdc++6
-            - fonts-droid
-      before_script:
-        - git clone --single-branch --branch stable https://github.com/flutter/flutter.git $HOME/flutter
-        - export PATH=$HOME/flutter/bin:$HOME/flutter/bin/cache/dart-sdk/bin:$PATH
-        - flutter doctor
-      script:
-        - flutter analyze
-    # Job 2) Build the Android axample application (.apk)
-    - os: linux
-      env:
-        - SHARD="Build example apks"
-      jdk: oraclejdk8
-      sudo: false
-      addons:
-        apt:
-          # Flutter depends on /usr/lib/x86_64-linux-gnu/libstdc++.so.6 version GLIBCXX_3.4.18
-          sources:
-            - ubuntu-toolchain-r-test # if we don't specify this, the libstdc++6 we get is the wrong version
-          packages:
-            - lib32stdc++6 # https://github.com/flutter/flutter/issues/6207
-            - libstdc++6
-            - fonts-droid
-      before_script:
-        - ./scripts/before_build_apks.sh
-        - export ANDROID_HOME=$HOME/android-sdk
-        - export PATH=$HOME/flutter/bin:$HOME/flutter/bin/cache/dart-sdk/bin:$PATH
-      script:
-        - cd ./example
-        - flutter build apk
-    # Job 3) Build the iOS example Applications (.ipa)
-    - os: osx
-      env:
-        - SHARD="Build example ipas"
-      language: generic
-      osx_image: xcode10.1
-      before_script:
-        - ./scripts/before_build_ipas.sh
-        - export PATH=$HOME/flutter/bin:$HOME/flutter/bin/cache/dart-sdk/bin:$PATH
-      script:
-        - cd ./example
-        - flutter build ios --no-codesign
-cache:
-  directories:
-    - $HOME/.pub-cache