Added Format and Analysis to CI, resolves #6 & #7

+os: linux
+dist: trusty
 sudo: true
+language: generic
 
 matrix:
-  exclude: # excluding Android test as Flutter seems to require Vulkan https://travis-ci.com/creativecreatorormaybenot/wakelock/jobs/214156381
-    - stage: Integration Testing
-
-      name: Android
-
-      os: linux
-      dist: trusty
-      language: android
+  include:
+    - stage: Check Format
 
-      android:
-        components:
-          - tools
-          - platform-tools
+      name: Dart code
 
-          - build-tools-28.0.3
-          - android-28
-          - android-24
+      install:
+        - git clone -b master https://github.com/flutter/flutter.git
+        - ./flutter/bin/flutter --version
+      before_script:
+        - export PATH="$PATH":"$HOME/.pub-cache/bin"
+        - export PATH=$PWD/flutter/bin:$PWD/flutter/bin/cache/dart-sdk/bin:$PATH
+      script:
+        - flutter format . --set-exit-if-changed --fix
 
-          - extra-google-m2repository
-          - extra-android-m2repository
+    - stage: Code analysis
 
-          - sys-img-armeabi-v7a-android-24
+      name: Dart code (plugin)
 
       install:
         - git clone -b master https://github.com/flutter/flutter.git
@@ -30,23 +28,28 @@ matrix:
       before_script:
         - export PATH="$PATH":"$HOME/.pub-cache/bin"
         - export PATH=$PWD/flutter/bin:$PWD/flutter/bin/cache/dart-sdk/bin:$PATH
+      script:
+        - flutter analyze
 
-        - echo no | android create avd --force -n test -t android-24 --abi armeabi-v7a
-        - emulator -avd test -no-window &
-        - android-wait-for-emulator
-        - adb shell input keyevent 82 &
+    - name: Dart code (example)
 
-        - flutter doctor -v
+      install:
+        - git clone -b master https://github.com/flutter/flutter.git
+        - ./flutter/bin/flutter --version
+      before_script:
+        - export PATH="$PATH":"$HOME/.pub-cache/bin"
+        - export PATH=$PWD/flutter/bin:$PWD/flutter/bin/cache/dart-sdk/bin:$PATH
 
         - cd example
       script:
-        - flutter driver test_driver/app.dart
-  include:
-    - name: iOS
+        - flutter analyze
+
+    - stage: Integration Testing
+
+      name: iOS
 
       os: osx
       osx_image: xcode10.2
-      language: generic
 
       before_install:
         - open /Applications/Xcode.app/Contents/Developer/Applications/Simulator.app
@@ -68,4 +71,42 @@ matrix:
 
         - cd example
       script:
+        - flutter driver test_driver/app.dart
+  exclude: # excluding Android test as Flutter seems to require Vulkan https://travis-ci.com/creativecreatorormaybenot/wakelock/jobs/214156381
+    - name: Android
+
+      os: linux
+      dist: trusty
+      language: android
+
+      android:
+        components:
+          - tools
+          - platform-tools
+
+          - build-tools-28.0.3
+          - android-28
+          - android-24
+
+          - extra-google-m2repository
+          - extra-android-m2repository
+
+          - sys-img-armeabi-v7a-android-24
+
+      install:
+        - git clone -b master https://github.com/flutter/flutter.git
+        - ./flutter/bin/flutter --version
+      before_script:
+        - export PATH="$PATH":"$HOME/.pub-cache/bin"
+        - export PATH=$PWD/flutter/bin:$PWD/flutter/bin/cache/dart-sdk/bin:$PATH
+
+        - echo no | android create avd --force -n test -t android-24 --abi armeabi-v7a
+        - emulator -avd test -no-window &
+        - android-wait-for-emulator
+        - adb shell input keyevent 82 &
+
+        - flutter doctor -v
+
+        - cd example
+      script:
         - flutter driver test_driver/app.dart
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