change the app color and fixe the text on the version button

src/css/index.styl

       &__submit
         &__btn
           display flex
+          border-color threadColor
           color off-white
-          background-color darkBlue
+          background-color threadColor
+          &:hover, &:focus
+            border-color darkenThread
+            background-color darkenThread
+            box-shadow shadow-all-side-thread
 
 .received
   text-align right

src/translate/fr.js

 const fr = {
   translation: { // 'fr' in the namespace 'translation'
     PopinFixedOption: {
-      new_version: 'test overrides trad from tracim_lib'
+      new_version: 'nouvelle version'
     }
   }
 }