update course Day 2

course/Day-2/presentation.cfg

+[darkslide]
+; the old [landslide] is still supported
+theme  = ../ptb_theme
+#source = ./
+source = 1-table-of-contents.md
+#         0-introduction.md
+#         1-table-of-contents.md
+#         2-day-1.md
+         3-day-2.md
+#         4-day-3.md
+destination = presentation.html
+#css =    my_first_stylesheet.css
+#         my_other_stylesheet.css
+#js =     jquery.js
+#         my_fancy_javascript.js
+relative = True
+linenos = inline
\ No newline at end of file