Added proper conversion for bigint() columns
Added proper conversion for bigint() columns

etehtsea/mysql-postgresql-converter,twillouer/mysql-postgresql-converter,BetterVoice/mysql-postgresql-converter,etehtsea/mysql-postgresql-converter,payplug/mysql-postgresql-converter,lanyrd/mysql-postgresql-converter,expa/mysql-postgresql-converter,gitlabhq/mysql-postgresql-converter,bignerdranch/mysql-postgresql-converter