Tidying up based on first contact with R maintainers.

1.  Renaming Ruby file to use underscore in name (consistent with other `bin` scripts).
2.  Generating `_includes/all_figures.html` for the first time when creating a new lesson.

Makefile

@@ -4,6 +4,7 @@
 # Settings
 MAKEFILES=Makefile $(wildcard *.mk)
 JEKYLL=jekyll
+PARSER=bin/markdown_ast.rb
 DST=_site
 
 # Controls
@@ -24,7 +25,7 @@ site :
 
 ## figures        : re-generate inclusion displaying all figures.
 figures :
-	@bin/extract_figures.py -s _episodes -p bin/markdown-ast.rb > _includes/all_figures.html
+	@bin/extract_figures.py -s _episodes -p ${PARSER} > _includes/all_figures.html
 
 ## clean          : clean up junk files.
 clean :
@@ -71,7 +72,7 @@ HTML_FILES = \
 
 ## lesson-check   : validate lesson Markdown.
 lesson-check :
-	@bin/lesson_check.py -s . -p bin/markdown-ast.rb
+	@bin/lesson_check.py -s . -p ${PARSER}
 
 unittest :
 	python bin/test_lesson_check.py

bin/lesson_initialize.py

@@ -315,6 +315,10 @@
 FIXME
 '''
 
+INCLUDES_ALL_FIGURES_HTML = '''\
+<!-- empty -->
+'''
+
 BOILERPLATE = (
     ('AUTHORS', ROOT_AUTHORS),
     ('CITATION', ROOT_CITATION),
@@ -327,7 +331,8 @@
     ('_extras/about.md', EXTRAS_ABOUT_MD),
     ('_extras/discuss.md', EXTRAS_DISCUSS_MD),
     ('_extras/figures.md', EXTRAS_FIGURES_MD),
-    ('_extras/guide.md', EXTRAS_GUIDE_MD)
+    ('_extras/guide.md', EXTRAS_GUIDE_MD),
+    ('_includes/all_figures.html', INCLUDES_ALL_FIGURES_HTML)
 )