Added payload_data 1-0-1 with new optional user agent field (#25)
Finalized date for R6
Merge branch 'feature/payload_data-1-0-1'
Fixed up CHANGELOG
Added: com.snowplowanalytics.snowplow/social_interaction/jsonschema/1-0-0 (closes #27)
Added add_to_cart and remove_from_cart schemas (closes #28 and closes #29)
Added elementContent field to link_click (closes #30)
Added schema for a submit_form event (closes #31)
Added schema for a change_form event (closes #32)
Added schema for a PerformanceTiming context (closes #33)
Added schema for a site_search event (closes #34)
Added Release 7 to CHANGELOG