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After experimenting with quip and qp for a few months, we seem to agree
that qp is a bit nicer to use. Remove quip, since it's largely redundant
going forward.

Since the qp docs referenced quip, redo that to stand on its own ground.

Since qp uses panics as an error mechanism, the top-level functions
recover those errors to return them normally.

However, this blows up if, internally, an ipld.Node implementation
panics with a value whose type is not error. For example, with:

	panic("some panic message")

One gets:

	panic: some panic message [recovered]
		panic: interface conversion: string is not error: missing method Error

Fix this by having a fallback for non-error panic values.

I started rewriting the "getting started" Go guide to use fluent/qp
instead of fluent, but I'm missing some of the helpers since the guide
uses links, among others.

This is largely copy-pasted, but there are just a handful of types and
it's barely a dozen lines per type. A generator is not worth it for 100
lines of code that will rarely ever need to change.

This is what I came up with, building on top of Eric's quip. I don't
want to waste too much time naming this, and I like two-letter package
names in place of dot-imports, so "qp" seems good enough for now. They
are the "strong" consonants when one says "Quick iPld".

First, move the benchmarks comparing all fluent packages to the root
fluent package, to keep things a bit more tidy.

Second, make all the benchmarks report their allocation stats, without
having to always remember to use the -benchmem flag.

Third, add a qp benchmark.

Fourth, notice a couple of potential bugs in the quip benchmarks, and
add TODOs for them.

Finally, add the qp API. It differs from quip in a few external ways:

1) No error pointers. Instead, it uses panics which are recovered at the
   top-level API layer. This reduces verbosity, removes the "forgot to
   handle an error" type of mistake, and does not affect performance
   thanks to the defers being statically allocated in the stack.

2) Supposed better composition. For example, one can use MapEntry along
   with Map to have a map inside another map. In contrast, quip requires
   either an extra layer of func literals, or extra API like
   AssignMapEntryString.

3) Thanks to the points above, the API is significantly smaller. Note
   that some helper APIs like Bool are missing, but even when added, qp
   should expose about half the API funcs taht quip does.

This is the first proof of concept. I'll probably finish adding the rest
of the API helpers when I find the first use case for qp.

Benchmark numbers, with perflock and benchstat on my i5-8350u laptop:

	name                              time/op
	Quip-8                            1.39µs ± 1%
	QuipWithoutScalarFuncs-8          1.42µs ± 2%
	Qp-8                              1.46µs ± 2%

	name                              alloc/op
	Quip-8                              912B ± 0%
	QuipWithoutScalarFuncs-8            912B ± 0%
	Qp-8                                912B ± 0%

	name                              allocs/op
	Quip-8                              18.0 ± 0%
	QuipWithoutScalarFuncs-8            18.0 ± 0%
	Qp-8                                18.0 ± 0%