let's have some fun with data structures.
add inspiration resources.
provide a Seq instance for the prelude list.
note some simple properties.

should we specify properties for take, drop, etc as well? because those
are defined on seq it doesn't seem "sensible", but could probably help
as well.
implement toList.
comment out (most likely) unused code.
allow overriding append.

by putting it back into the Seq type class. the same would be possible
for all those functions defined on Seq, but i don't want to put that
many things in there. later, maybe?

(one way to make all those functions overridable is by making a type
class for each of them and adding a default instance that does what they
currently do. is there an extension for these "extendable" functions?
there probably is.)
add 2-3 fingertree implementation.

"very, very slow", says daniel spiewak. we'll find out why later.