Order[A] now implements eqv() in terms of compare().

Previously, we left eqv() unimplemented. The rationale behind that no
longer makes sense, so now we provide an implementation and require
the user to override it if desired.

This change ended up touching every file that defines an Order or Eq,
but fortunately the required changes were minor.
Move log from NRoot to Trig
specialize on Byte/Short, clean up a bit
Remove unused Conversions support
Remove Gaussian and EuclideanRational from spire.math
Standardize spire.math to include more functions.

The goal eventaully is to make importing from scala.math (or
java.lang.Math) obsolete. This commit adds abs/ceil/floor and fleshes
out some other useful cases.
Fix bug in shifting UByte/UShort + clean up
Add support for sampling and shuffling.

Using the Shuffling and Sampling objects from Spire, we now support
the following:

  arr.qshuffle()  // in-place array shuffle
  ns.qshuffled    // returns new shuffled collection
  ns.qchoose      // choose a random element from any Iterable
  ns.qsampled(10) // returns 10 random elements in an array

You will need an implicit spire.random.Generator instance in scope
to use these methods (possibly we should put spire.random.GlobalRng
in the default global scope).
Use spire.random.GlobalRng as an implicit Generator
Remove {Left,Right}Module, as we don't use them.
Move shuffling and sampling into spire.random.Generator.

Previously we had some stand-alone objects but the RNG seemed like a
better place to put these. Of course, methods are still implicitly
added to collections via spire.implicits.

Sampling may be moved out into a type class but for now it will live
in the Generator.
Merge remote-tracking branch 'tixxit/topic/module-simplification' into 2.10.0
Updates to spire.random

This commit renames Next[A] to Dist[A] and adds some more useful
methods. The API is still evolving and may end up going in a different
direction eventually.
fix bug in SeqOps#qmean
add Natural.apply for String input
add Integral[SafeLong] instance
Fix super + specialization bug.

Wookie Treiber noticed a specialization bug (causing infinite recursion)
in Integral#fromInt. This commit stops using super in cases where it
may cause this problem.

Version is bumped to 0.4.0-M3.

Fixes #86