Rename cost to hourly_cost

As it better describes what it does. It calculates hourly cost for a
given metric.

app/models/chargeback.rb

@@ -146,7 +146,7 @@ def calculate_costs(metric_rollup_records, rates, hours_in_interval)
  else
  r.hours_in_interval = hours_in_interval
  metric_value = r.metric_value_by(metric_rollup_records)
- cost = r.cost(metric_value) * hours_in_interval
+ cost = r.hourly_cost(metric_value) * hours_in_interval
  end
 
  accumulate_metrics_and_costs_per_rate(r.rate_name, r.group, metric_value, cost)

app/models/chargeback_rate_detail.rb

@@ -74,7 +74,7 @@ def find_rate(value)
  :yearly => "Year"
  }
 
- def cost(value)
+ def hourly_cost(value)
  return 0.0 unless self.enabled?
 
  value = 1.0 if fixed?

spec/models/chargeback_rate_detail_spec.rb

@@ -26,7 +26,7 @@
 
  let(:hours_in_month) { 720 }
 
- it "#cost" do
+ it '#hourly_cost' do
  cvalue = 42.0
  fixed_rate = 5.0
  variable_rate = 8.26
@@ -46,13 +46,13 @@
  :fixed_rate => fixed_rate,
  :variable_rate => variable_rate)
  cbd.update(:chargeback_tiers => [cbt])
- expect(cbd.cost(cvalue)).to eq(cvalue * cbd.hourly(variable_rate) + cbd.hourly(fixed_rate))
+ expect(cbd.hourly_cost(cvalue)).to eq(cvalue * cbd.hourly(variable_rate) + cbd.hourly(fixed_rate))
 
  cbd.group = 'fixed'
- expect(cbd.cost(cvalue)).to eq(cbd.hourly(variable_rate) + cbd.hourly(fixed_rate))
+ expect(cbd.hourly_cost(cvalue)).to eq(cbd.hourly(variable_rate) + cbd.hourly(fixed_rate))
 
  cbd.enabled = false
- expect(cbd.cost(cvalue)).to eq(0.0)
+ expect(cbd.hourly_cost(cvalue)).to eq(0.0)
  end
 
  it "#hourly" do
@@ -195,7 +195,7 @@
  :per_time => 'monthly',
  :chargeback_rate_detail_measure_id => cbdm.id,
  :hours_in_interval => hours_in_month)
- expect(cbd_bytes.cost(100)).to eq(cbd_gigabytes.cost(100))
+ expect(cbd_bytes.hourly_cost(100)).to eq(cbd_gigabytes.hourly_cost(100))
  end
 
  it "#show_rates" do