Remove private attr_readers

It was an experiment following @avdi's advice to wrap constants,
instance variables etc so their implementation could be changed without
having to replace all references, but doesn't seem to add much value
here.
Remove unused exception variable
Switch to Ruby 2.0.0
Update status asynchronously
Feature for winning auction (with pending steps)
Implement 'I am told that I am the high bidder' step
Poll more aggressively in tests
Move EM start/stop back out of app again (I'll make my mind up eventually)
Failing step for 'should have won'
Add bugs section to readme
Wait for 'winning' status in test
Disable ye olde rspec 'should' syntax
Enable colour in rspec
Add price source to auction event listener (symbols though, not enums)
Add guard
Handle price source (sniper or other bidder)

Removed role specs for doubles, which caused more problems than it
solved.  By forcing the double to stub all methods in the role, it hid
errors caused by calling methods that we shouldn't have.
Remove the other double role spec, and only stub what we expect