Make the build Python-2/3 agnostic.

INSTALL.adoc

@@ -1,5 +1,9 @@
 = Installing Open Adventure =
 
+The instructions below assume your system uses Python 3 by default,
+but the actual Python code in Open Adventure is 2/3 agnostic. Adjust
+the example commands below accordingly.
+
 1. Install PyYAML for Python 3 (which requires Python 3), and libedit
 (aka: editline) on your system.
 

Makefile

@@ -40,7 +40,7 @@ dungeon.o:	dungeon.c dungeon.h
 	$(CC) $(CCFLAGS) $(DBX) -c dungeon.c
 
 dungeon.c dungeon.h: make_dungeon.py adventure.yaml
-	python3 make_dungeon.py
+	./make_dungeon.py
 
 clean:
 	rm -f *.o advent cheat *.html *.gcno *.gcda

make_dungeon.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python
 
 # This is the open-adventure dungeon generator. It consumes a YAML description of
 # the dungeon and outputs a dungeon.h and dungeon.c pair of C code files.