Fix / upd: properties declared on parent after inheritance takes place are now passed to children

[jorroll]

I'm not sure if this is a bug or intended behavior, but currently: if an ActiveNode class A is inherited by B, and then an ActiveNode property is subsequently declared on A, B will not have that property (i.e. properties are only be transferred at inheritance).

This PR makes it so that every property declared on a parent is also present on the children (unless undef_property was explicitly called on a child).

In achieving this, I plucked ActiveSupport/core_ext/class/subclasses and added the subclasses method to Class.

This pull introduces/changes:

• properties declared on parent classes after inheritance has taken place are properly inherited by subclasses
• all classes now have subclasses method

Example

class Person
  include Neo4j::ActiveNode

  class Superhero < Person
  end

  property :name
end

hero = Person::Superhero.new
hero.name = 'John'
hero.name
#=> 'John'

Pings:
@cheerfulstoic
@subvertallchris

[jorroll]

This PR has a minor conflict with #1419

[codecov-io]

Codecov Report

Merging #1428 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1428      +/-   ##
==========================================
+ Coverage   96.81%   96.81%   +<.01%     
==========================================
  Files         205      205              
  Lines       12511    12539      +28     
==========================================
+ Hits        12112    12140      +28     
  Misses        399      399

Impacted Files	Coverage Δ
lib/neo4j/shared/enum.rb	98.66% <100%> (+0.03%)	⬆️
lib/neo4j/shared/property.rb	97.54% <100%> (+0.06%)	⬆️
spec/e2e/inheritance_spec.rb	100% <100%> (ø)	⬆️
lib/neo4j.rb	97.95% <100%> (+0.02%)	⬆️

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[jorroll]

I suppose this update has the capacity to break things... If it is something you're interested in accepting, might be a good idea to release it along with #1419

[cheerfulstoic]

Thanks so much for this! I would say this falls into the bugfix camp, but I'll release it in 9.0.0 just to make sure. I resolved the conflict and now waiting for Travis to finish before merging (though I might not get back to it this evening)

[jorroll]

awesome

[cheerfulstoic]

9.0.0 released

[jorroll]

Whoo hoo