Make the default (translated) error configurable both globally and on each instance.
Only load RSpec custom matchers if they are in use.

A user may have overridden the default RSpec matchers in favor of another library (Mocha, RR, etc.)
Merge branches 'configure_default_error' and 'support-rspec-custom-matchers' into all-change-branches
Merge pull request #1 from change/all-change-branches

All change branches