Delete minus1Trunc.v, close #434

 @brunobarras did some work on logic for general modalities already.
However, it may be easier to redo it, then to try to resurrect his code, I
don't know.
https://github.com/HoTT/HoTT/tree/hott-on-generic-equality
- the file coq/theories/Init/LogicClasses that defines empty typeclasses
gathering information about the logics
- how they are used to declare one´s own logic (e.g. theories/Paths)
- a quick implementation of tauto based on these logics (contrib/test-suite)

On Thu, Sep 18, 2014 at 7:38 PM, Mike Shulman <notifications@github.com>
wrote:

> In theories/hit/quotient.v:
>
> > @@ -179,10 +179,12 @@ intros. apply Hprop'.
> >  Defined.
> >
> >  (** From Ch6 *)
> > -Theorem quotient_surjective: issurj (class_of _).
> > -unfold issurj. apply (quotient_ind (fun y => hexists (fun x : A => class_of R x = y))).
> > - apply _.
> > -intro x. apply min1. by exists x.
> > +Theorem quotient_surjective: IsSurjection (class_of _).
> > +Proof using A R sR.
>
> It became one line longer. That one line is because I changed the
> definition of IsSurjection to be a special case of IsConnMap, so that it
> asserts contractibility of the truncation of the fibers rather than
> inhabitation. However, on reflection, the equivalence of that with the
> simpler definition (in the case -1) should probably be split out into its
> own lemma.
>
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