v0.2.42

Cleaner Topic Guides navigation. A few improvements to reading topic guides:

• The topic list no longer covers the guide. Click the Topic Guides title at the top (note the
  little ▾) any time to slide open the searchable list; it tucks away again as soon as you pick a
  topic. It also starts closed now — so when you jump straight to a guide from a flashcard or a
  question explanation, you land right on the content, with nothing in the way.
• The ← Back button shows where it'll take you on a small second line — to Practice, to Exam,
  to Review, or to Home — so you always know where you'll land before tapping it.