Add f-droid and twitter badges

Closes #4 (closed)

css/styles.css

@@ -29,7 +29,13 @@ img {
     vertical-align:middle;
 }
 
-#playbutton {
+#twitterbutton {
+    width: 21px;
+    padding-left: 9px;
+    padding-top: 3px;
+}
+
+#playbutton, #fdroidbutton {
     width:240px;
 }
 
@@ -511,7 +517,7 @@ figcaption {
         margin-top:15px;
     }
 
-    #playbutton {
+    #playbutton, #fdroidbutton {
         width:200px;
     }