Upgrade to RSpec 3.0.

Resolves #145.
Update specs for the latest RSpec syntax changes.

Use `expect().to receive` for expectations.
Use `allow/expect.to receive` for stubs and mocks.
Switch to `be_true` the new `be_truthy` matcher to fix failures.
Fix pending and too long lines
Merge pull request #1 from tlunter/rspec3

Fix pending and too long lines
Merge pull request #146 from tylerhunt/rspec3

Upgrade to RSpec 3.0