Merge branch 'master' into smarter-imports

# Conflicts:
#	src/module/io.c
#	src/vm/wren_vm.c

Makefile

@@ -90,6 +90,7 @@ unit_test:
 
 # Generate the Wren site.
 docs:
+	mkdir -p build
 	$(V) ./util/generate_docs.py
 
 # Continuously generate and serve the Wren site.