Naming conventions
Added X-Rate-Limit-Period header
Corrected tests for naming conventions
Test for period header
Updated README
Undo header name changes
Merge branch 'pr/3' into period_header

Conflicts:
README.md
lib/rack/attack/rate-limit.rb
spec/rack/attack/rate-limit_spec.rb
Merge branch 'pr/3'

Conflicts:
	README.md
	lib/rack/attack/rate-limit.rb
	spec/rack/attack/rate-limit_spec.rb