banana-bread.md: Adjust headings

GitHub wraps rendered Markdown in HTML5 <article> tags so they can
be top-level headings.

Signed-off-by: Alan Orth <alan.orth@gmail.com>

banana-bread.md

@@ -1,8 +1,8 @@
-## Banana bread
+# Banana bread
 
 Originally from: http://www.simplyrecipes.com/recipes/banana_bread/
 
-### INGREDIENTS
+## INGREDIENTS
 
 - 3 or 4 ripe bananas, mashed
 - 1/3 cup melted butter
@@ -15,6 +15,6 @@ Originally from: http://www.simplyrecipes.com/recipes/banana_bread/
 - Handful of walnut pieces (optional)
 - Ground flax seed (optional)
 
-### METHOD
+## METHOD
 
 No need for a mixer for this recipe. Preheat the oven to 350°F (175°C). With a wooden spoon, mix butter into the mashed bananas in a large mixing bowl. Mix in the sugar, egg, and vanilla. Sprinkle the baking soda and salt over the mixture and mix in. Add the flour last, mix. Pour mixture into a buttered 4x8 inch loaf pan. Bake for 1 hour. Cool on a rack. Remove from pan and slice to serve.