allow string keys in config hash
Guard me from myself!
update rubocop and rspec

RSpec 3 changed the way mocks and stubs syntax is handled, and set a config
option used here to default to true.

Left a TODO for method complexity during refactor.
ignore Appraisal-generated lock files
update Appraisals for current versions
Merge branch 'initialize-config-strings' of from @dwradcliffe
docs update