Update rspec version

[at1as]

Hi, I noticed that$ bundle install is no longer working because a Rake method that is being called by rspec-core was renamed from last_comment to last_method.

The pinned version of rpsec, 2.12.0 continues to call Rake.application.last_comment, which was renamed to Rake.application.last_description, in the version of Rake that we're pulling.

See: rspec/rspec-core@8e723fc for the commit that introduces the change, which was part of rspec 3.5.0.

Jasons-MacBook-Pro-3:em-websocket atlas$ rake
rake aborted!
NoMethodError: undefined method `last_comment' for #<Rake::Application:0x007fef231601d8>
/Users/atlas/.rvm/gems/ruby-2.4.0/gems/rspec-core-2.12.2/lib/rspec/core/rake_task.rb:119:in `initialize'
/Users/atlas/Repos/em-websocket/Rakefile:6:in `new'
/Users/atlas/Repos/em-websocket/Rakefile:6:in `<top (required)>'
/Users/atlas/.rvm/gems/ruby-2.4.0/gems/rake-12.3.0/exe/rake:27:in `<top (required)>'
/Users/atlas/.rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `eval'
/Users/atlas/.rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `<main>'
(See full trace by running task with --trace)

After pinning rspec to 3.5.0 there was also one test error when running rake:

Failures:

  1) WebSocket server outbound limit set should close the connection if the limit is reached
     Failure/Error: status[:was_clean].should be_false
       expected false to respond to `false?` or perhaps you meant `be false` or `be_falsey`
     # ./spec/integration/common_spec.rb:120:in `block (6 levels) in <top (required)>'
     # ./lib/em-websocket/connection.rb:27:in `call'
     # ./lib/em-websocket/connection.rb:27:in `trigger_on_close'
     # ./lib/em-websocket/handler.rb:83:in `unbind'
     # ./lib/em-websocket/connection.rb:105:in `unbind'
     # /Users/atlas/.rvm/gems/ruby-2.2.4/gems/eventmachine-1.2.5/lib/eventmachine.rb:1483:in `event_callback'
     # /Users/atlas/.rvm/gems/ruby-2.2.4/gems/eventmachine-1.2.5/lib/eventmachine.rb:194:in `run_machine'
     # /Users/atlas/.rvm/gems/ruby-2.2.4/gems/eventmachine-1.2.5/lib/eventmachine.rb:194:in `run'
     # /Users/atlas/.rvm/gems/ruby-2.2.4/gems/em-spec-0.2.7/lib/em-spec/rspec.rb:26:in `em'
     # ./spec/integration/common_spec.rb:114:in `block (3 levels) in <top (required)>'

The tweak in the test case included in the PR fixes it. I tested this on ruby 2.2 and 2.4:

$ rake
...
Finished in 2.61 seconds (files took 0.43348 seconds to load)
184 examples, 0 failures

[igrigorik]

Great work, thanks for the update!