Edit Makefile.

Change documentation rules. 'doc' target no longer creates PDFs from
markdown files. The 'markdown' target provides this.
Move markdown to markdown dir. Edit doc/module.mk to reflect change.
Rename SLog to Slog. Reorganize.
Add time.hpp for formatting date-time strings.
time compiles.
Edit DailyLogWriter to use new time stuff.
Edit everything. Now compiles with the new time functionality.
Finish unit tests so they compile.
Edit test/.gitignore
Built. Test suite seg-faulting.
Ton of edits. Finish time.cpp
Test everything is good except time functions. Time functions return
weird values.
Finish time for now.