Move unused figures to fig/ too.

diff --git a/asynch.pdf b/fig/asynch.pdf
similarity index 100%
rename from asynch.pdf
rename to fig/asynch.pdf

diff --git a/asynch_tasks.pdf b/fig/asynch_tasks.pdf
similarity index 100%
rename from asynch_tasks.pdf
rename to fig/asynch_tasks.pdf

diff --git a/synch_tasks.pdf b/fig/synch_tasks.pdf
similarity index 100%
rename from synch_tasks.pdf
rename to fig/synch_tasks.pdf