Update rspec matcher failure interface for rspec 3

Updates the rspec matcher interface to use failure_message_when_negated
instead of negative_failure_message.

Fixes several deprecation warnings while running the test suite.
Fix Rspec stub deprecation warning message

In RSpec 3 it is deprecated to use Object#stub without enabling the
should syntax.
Merge pull request #732 from lengarvey/fix_rspec_3_deprecations

Fix some rspec 3 deprecations