Debug log should convert Date instance to calendar date format

[garethrees]

When supplying Date instances to the API, the log message appears with human readable date: :startdate=>Sun, 10 Jun 2018. This is a little confusing, as it doesn't look like a valid parameter.

irb(main):006:0> Infreemation::Request.where(rt: 'published', startdate: '2018-06-01', enddate: '2018-06-30')
GET /foi/ with {:rt=>"published", :startdate=>"2018-06-01", :enddate=>"2018-06-30"}

    { "status": "OK", "ref": "0", "error": "No data is available" }

=> []

irb(main):006:0> Infreemation::Request.where(rt: 'published', startdate: 1.month.ago.to_date, enddate: Time.zone.now.to_date)
GET /foi/ with {:rt=>"published", :startdate=>Sun, 10 Jun 2018, :enddate=>Tue, 10 Jul 2018}

    { "status": "OK", "ref": "0", "error": "No data is available" }

=> []