Test updates and beta node size

I pulled in the beta_node size method from [https://github.com/ulfurinn/wongi-engine/issues/25] and I updated a number of the tests that passed while running rspec, but failed with rake. I basically just updated the syntax from should to: 
```ruby
expect(some thing).to eq(whatever)
```
These were low hanging syntax things, but I hope to follow up later with more test suite improvements.

I also updated some of the tests to reflect the beta_node.size method.