generate ActivityField
add attr_accessible and validations to activity_field
remove the content field and the has_one relationship with activity_field
delete old script/rails
remove app:spec
add some initial model test for ActivityField
change activity.content to activity.activity_field.content
don't build the activity_field if the share has no content
Merge pull request #75 from acmetech/master

Move the Activity content column to a new ActivityField model