Remove Travis integration

.travis.yml

@@ -1,48 +0,0 @@
-# based on https://gist.github.com/KNawm/9c7c7963e7f772d6d5172fe9da7ce79b
-language: generic
-dist: bionic
-addons:
-    apt:
-        packages:
-            - lib32stdc++6
-env:
-    global:
-        - FLUTTER_CHANNEL=stable
-install:
-    - git clone https://github.com/flutter/flutter.git -b $FLUTTER_CHANNEL
-    - export PATH=$(pwd)/flutter/bin:$PATH
-    - export PATH=$(pwd)/flutter/bin/cache/dart-sdk/bin:$PATH
-    - flutter doctor -v
-    - flutter pub get
-    - flutter pub upgrade
-    - flutter packages pub run build_runner build --delete-conflicting-outputs
-
-static_analysis: &static_analysis
-    name: "Static analysis"
-    script: flutter analyze --no-current-package $TRAVIS_BUILD_DIR/lib
-
-#build: &build
-#  name: "Build APK"
-#  language: android
-#  android:
-#    components:
-#      - tools
-#      - tools
-#      - platform-tools
-#      - build-tools-28.0.3
-#      - android-28
-#  before_script:
-#    - export BUILD_NAME=$TRAVIS_TAG
-#    - export BUILD_NUMBER=$TRAVIS_BUILD_NUMBER
-#  script:
-#    - jdk_switcher use openjdk8
-#    - if [[ $TRAVIS_TAG == "" ]]; then flutter build apk; else flutter build apk --build-name $BUILD_NAME --build-number $BUILD_NUMBER; fi
-
-jobs:
-    include:
-        -   <<: *static_analysis
-#    - stage: build
-#      <<: *build
-cache:
-    directories:
-        - $HOME/.pub-cache