Update event registration email text
Update event registration email text

Fixes #1050

azavea/nyc-trees,azavea/nyc-trees,azavea/nyc-trees,kdeloach/nyc-trees,maurizi/nyc-trees,kdeloach/nyc-trees,azavea/nyc-trees,kdeloach/nyc-trees,kdeloach/nyc-trees,maurizi/nyc-trees,kdeloach/nyc-trees,maurizi/nyc-trees,maurizi/nyc-trees,azavea/nyc-trees