Covert arrays to to postgres style arrays

Currently, arrays are transformed into a string with the following format: '[elem1, elem2]'.

Unfortunately, Postgres wants you to use curly braces for arrays (for example, '{elem1, elem2}') and the current implementation throws an error when trying to execute an insert/update on columns with an array type.

This change uses a helper method from Sequel to convert an array to a Postgres compatible array.

Postgres Arrays docs:
http://www.postgresql.org/docs/9.3/static/arrays.html

Sequel pg_array docs:
http://sequel.jeremyevans.net/rdoc-plugins/files/lib/sequel/extensions/pg_array_rb.html