Merge branch '5-improve-layout' into 'master'

Resolve "Improve layout"

Closes #5

See merge request !6

android/gradle.properties

 org.gradle.jvmargs=-Xmx1536M
 android.useAndroidX=true
 android.enableJetifier=true
-app.versionName=1.1.0
-app.versionCode=3
+app.versionName=1.1.1
+app.versionCode=4

lib/main.dart

@@ -152,13 +152,13 @@ class _MyHomePageState extends State<MyHomePage> {
               children: <Widget>[
                 Text(
                   'Lettre aléatoire :',
-                  style: Theme.of(context).textTheme.headline3,
+                  style: Theme.of(context).textTheme.headline4,
                 ),
                 Text(
                   '$_randomLetter',
-                  style: Theme.of(context).textTheme.headline4,
+                  style: Theme.of(context).textTheme.headline2,
                 ),
-                FlatButton(
+                RaisedButton(
                   onPressed: _pickRandomLetter,
                   color: Colors.orange,
                   padding: EdgeInsets.all(10.0),
@@ -171,16 +171,17 @@ class _MyHomePageState extends State<MyHomePage> {
                 ),
               ],
             ),
+            SizedBox(height: 50),
             Column(
               mainAxisAlignment: MainAxisAlignment.center,
               children: <Widget>[
                 Text(
                   'Catégorie aléatoire :',
-                  style: Theme.of(context).textTheme.headline3,
+                  style: Theme.of(context).textTheme.headline4,
                 ),
                 Text(
                   '$_randomCategory',
-                  style: Theme.of(context).textTheme.headline4,
+                  style: Theme.of(context).textTheme.headline3,
                 ),
                 FlatButton(
                   onPressed: _pickRandomCategory,