Add an overarching goal paragraph.

README.md

@@ -1,3 +1,15 @@
 I'm told this is a giant pile of code which might seem unapproachable.  So as
 a brief guide I would start with `NOTES.md` and then look at the top half of
 `lpset.nim`.  `TODO.md` also has a lot of notes in it.
+
+My overarching goal/vision is to allow "the fast way" most of the time,
+especially for developers that might know how to provide a good `hash`,
+but to also have auto fall backs to "safer ways" with optional messages to
+let developers know they might want to intervene by changing some defaults at
+table construction time (or else let users/sysadmins know that some input may
+be violating the assumptions of some code sensitive to inputs).  I think this
+may be a thing that commercial database systems have done for decades, but
+hasn't really percolated into commonly available runtime libraries.  (Depth
+based growth trigger is probably the simplest example of a profile-guided
+optimization for data structures.  A.Dain Samples 1993 PhD thesis has some
+more.)