Clarified and aligned PartialOrder semantics to Order semantics: the only allowed values for partialCompare are -1.0, 0.0, 1.0 and NaN.
Shortened the pmin and pmax methods using these assumptions.
Removed the tryLteqv, tryGteqv, tryGt, tryLt that do not have corresponding operators (they can be easily implemented using tryCompare).
Updated GUIDE.md and README.md to include PartialOrder.
Reverted some changes as not to depend on partialCompare being exactly -1.0, 0.0, 1.0.
Merge pull request #293 from denisrosset/topic/partial-order-doc

A few bugfixes for PartialOrder, and update of documentation
Removed scalar from GroupAction.
Semigroup scalar is not available anymore in the GroupAction instance.
Add Ziggurat Exponential generator to CHANGES.md
Merge pull request #300 from dusank/topic/Fix-CHANGES.md

Add Ziggurat Exponential generator to CHANGES.md
Removed scalar from SignAction and Torsor.
Merge pull request #299 from denisrosset/topic/remove-action-scalar

Topic/remove action scalar
Pedantically correct spelling in User's Guide

…though it warms my heart that the letter order was reversed in a sentence explaining the reversed order of *Order explanations.
Merge pull request #302 from barnardb/patch-1

Pedantically correct spelling in User's Guide
Correct a few errors in the User's Guide

I can't tell from a quick glance at the implementation whether the bounds of the image of atan2 are theoretically open or closed, so I went with open-closed as it is often defined, even though in practice results can compare equal to -pi.
Merge pull request #303 from barnardb/patch-2

Correct a few errors in the User's Guide
compute complex norm in a way that does not overflow. add test for this
add hypot function that works on all types
make complex norm use hypot to eliminate redundant code
use aggregate instead of foldLeft in Σ and Π
Monoid.sum can also be implemented in terms of aggregate (vs reduce)
Revert "Monoid.sum can also be implemented in terms of aggregate (vs reduce)"

This reverts commit efc1c60a4332658c2141917965b011947a6cfebf.