Fix behaviour of Brex.none

Changed

• BREAKING: Brex.none now only succeeds if every rule fails (before it only already succeeded when a single rule failed)

Make compatible with Elixir 1.10

See #5 for details, much thanks to @lorenzosinisi

Fix critical compilation issue

Version v0.2.1 failed to compile due to the version file missing from the hex package. This version includes the file in the package and also loads it into a module attribute instead of loading it at runtime.

Fix Brex.none/1 behaviour for empty lists

The behaviour of Brex.none/1 was confusing for an empty list of rules, due to simply inverting the result of Brex.all/1. This release introduces a special handling for an empty list of rules:

Before

iex> rules |> Brex.none() |> Brex.satisfies?(:whatever)
false

After

iex> rules |> Brex.none() |> Brex.satisfies?(:whatever)
true

Simplify custom operator creation

This release introduces a greatly simplified Operator generation. I've realised that the former implementation basically was reimplementing structs in a shitty manner. As such the Brex.Operator is now simply a struct with an aggregator and a clauses field.

For details take a look at the Brex.Operator moduledocs.