clean up the layout & polished Mensa credit dialog

* don't crash if the nfc tag has been removed between triggering intent and connecting to the tag
* closes #21

build.gradle

@@ -1,13 +1,13 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.3.40'
+    ext.kotlin_version = '1.3.50'
     repositories {
         google()
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.4.2'
+        classpath 'com.android.tools.build:gradle:3.5.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong