Use 7zip on Windows

Makefile

@@ -10,6 +10,12 @@ INSTALL_DATA = $(INSTALL) -m 644
 
 prefix = /usr/local
 
+ifeq ($(OS), Windows_NT)
+	ZIP_PROGRAM=7z a -r
+else
+	ZIP_PROGRAM=zip -r -9
+endif
+
 # ifdef check allows the user to pass custom dirs
 # as per the README
 
@@ -54,7 +60,7 @@ dist: $(DISTFILES) todo.sh
 	chmod +x "$(DISTNAME)/todo.sh"
 	tar cf $(DISTNAME).tar "$(DISTNAME)"
 	gzip -f -9 "$(DISTNAME).tar"
-	zip -r -9 "$(DISTNAME).zip" "$(DISTNAME)"
+	$(ZIP_PROGRAM) "$(DISTNAME).zip" "$(DISTNAME)"
 	rm -r "$(DISTNAME)"
 
 .PHONY: clean
@@ -66,7 +72,7 @@ install: installdirs
 	$(INSTALL_PROGRAM) todo.sh "$(DESTDIR)$(bindir)/todo.sh"
 	$(INSTALL_DATA) todo_completion "$(DESTDIR)$(datarootdir)/todo"
 	[ -e "$(DESTDIR)$(sysconfdir)/todo/config" ] || \
-	    sed "s/^\(export[ \t]*TODO_DIR=\).*/\1~\/.todo/" todo.cfg > "$(DESTDIR)$(sysconfdir)/todo/config"
+		sed "s/^\(export[ \t]*TODO_DIR=\).*/\1~\/.todo/" todo.cfg > "$(DESTDIR)$(sysconfdir)/todo/config"
 
 uninstall:
 	rm -f "$(DESTDIR)$(bindir)/todo.sh"
@@ -78,8 +84,8 @@ uninstall:
 
 installdirs:
 	mkdir -p "$(DESTDIR)$(bindir)" \
-	         "$(DESTDIR)$(sysconfdir)/todo" \
-	         "$(DESTDIR)$(datarootdir)"
+			 "$(DESTDIR)$(sysconfdir)/todo" \
+			 "$(DESTDIR)$(datarootdir)"
 
 #
 # Testing