Added some more interaction helpers

Re #95 

Adds count helpers. Had to fix capybara webkit to an older version but seems to work fine.

Allows you now to do things like:

```ruby
@event.confirmed_tickets_count #=> counts number of current interactions on relation 'tickets' with type 'confirmed' 
@event.confirmed_and_attending_tickets_count #=> same as above but counts 2 types
@event.confirmed_and_not_attending_tickets_count #=> allows for mixing in "not"
@event.all_tickets_counts #=> returns a hash with all current counts
```

All of these count current records with the value set to true.