Bump RSpec to 3.1 and disable RSpec monkey patching
Update RSpec syntax to 3.x style

Obj.stub -> allow(Obj).to receive(:foo)
should -> expect syntax

This disables RSpec monkey patching per
https://www.relishapp.com/rspec/rspec-core/v/3-1/docs/configuration/zero-monkey-patching-mode
Specify bundler ~> 1.6 to fix TravisCI builds

TravisCI only has bundler 1.6 so the build fails since the dependency
was ~> 1.7. There is no real reason we have to have bundler 1.7.
Merge pull request #122 from Nordstrom/rspec3

Upgrade to RSpec 3.1 and disable monkey-patching