Downgrade multi_json temporarily

Gemfile set to downgrade multi_json to eliminate spurious error
messages. Waiting for upgrade to fix bug then remove downgraded gem
specification.
Addresses included in elasticsearch index

Include addresses in to_json call for elasticsearch.
Rake task to import contacts

We scoped contacts by Account.id. This breaks importing rake tasks
provided by tire gem. This rake task simply imports all contacts.
Due date with datepicker

Added due date field to contact model. People/Companies#show uses
best_in_place datepicker to edit due date.
Common #show view code moved to partials

Companies and people #show views use identical code. Moved the code into
two partials to simplify updates.