Remove Virtus

[orien]

Convert Event to a plain old Ruby object. This was the only thing using Virtus, so we can now remove it as a dependency.

[stevehodgkiss]

Looks good. We just need to add some equality methods (I know some specs in Identity will fail without #==, #eql? etc). Here's what Virtus is adding in:

irb(main):013:0> puts EventSourcery::Event.new.method(:==).source
    def ==(other)
      other = coerce(other).first if respond_to?(:coerce, true)
      other.kind_of?(self.class) && cmp?(__method__, other)
    end
=> nil
irb(main):014:0> puts EventSourcery::Event.new.method(:eql?).source
    def eql?(other)
      instance_of?(other.class) && cmp?(__method__, other)
    end
=> nil
irb(main):015:0> puts EventSourcery::Event.new.method(:cmp?).source
    define_method(:cmp?) do |comparator, other|
      keys.all? do |key|
        __send__(key).public_send(comparator, other.__send__(key))
      end
    end
=> nil

[orien]

Thanks @stevehodgkiss. I was going to ask about those.

[orien]

Seems strange to inspect all attributes of an object which has specific identifier attributes.

I propose using id for ordering comparisons, <, <=, ==, >=, >. Whereas the eql? method can use uuid and instance type for its comparison.

@stevehodgkiss Will this satisfy Identity's use case?

[orien]

I used a Ruby feature introduced in 2.3.0. Ok to lock EventSourcery to Ruby 2.3.0 or higher?