Improve documentation readability
Improve documentation readability

Adds definite and indefinite articles where appropriate, and fixes tense to improve consistency and overall readability of the documentation. No changes to the code examples.
arkency/rails_event_store,RailsEventStore/rails_event_store,mpraglowski/rails_event_store,arkency/rails_event_store,mpraglowski/rails_event_store,RailsEventStore/rails_event_store,mpraglowski/rails_event_store,RailsEventStore/rails_event_store,RailsEventStore/rails_event_store,mpraglowski/rails_event_store,arkency/rails_event_store,arkency/rails_event_store