Change deprecated matcher that were warned by RSpec 2.99

be_true
  => be true
be_false
  => be false
expect(list).to have(N).elements
  => expect(list.size).to eq N
Convert specs to RSpec 2.14.7 syntax with Transpec

This conversion is done by Transpec 1.5.1 with the following command:
    transpec

* 17 conversions
    from: obj.stub(:message)
      to: allow(obj).to receive(:message)

* 4 conversions
    from: obj.should_receive(:message)
      to: expect(obj).to receive(:message)

* 3 conversions
    from: obj.should
      to: expect(obj).to

* 3 conversions
    from: obj.should_not_receive(:message)
      to: expect(obj).not_to receive(:message)
Update list of supported rubyies
Merge pull request #34 from gongo/preparation_migrate_to_rspec3

Support RSpec 3