Posgra doesn't work with ruby-pg v1.5.0 onwards

[hfm]

Since ruby-pg v1.5, PG::Connection::CONNECT_ARGUMENT_ORDER has become private_constant by ged/ruby-pg#522. As a result, posgra raises errors as follows when connecting to postgres.

NameError:
  private constant PG::Connection::CONNECT_ARGUMENT_ORDER referenced

posgra/lib/posgra/client.rb

Line 337 in 375173d

PG::Connection::CONNECT_ARGUMENT_ORDER.each do |key|