Return a string from display_days_before_maturity

Sometimes we were returning a string, and sometimes we were returning an
integer. We're only ever displaying the result, and this seems a little
more consistent.

app/helpers/plantings_helper.rb

@@ -1,13 +1,13 @@
 module PlantingsHelper
   def display_days_before_maturity(planting)
     if planting.finished?
-      0
+      "0"
     elsif !planting.finished_at.nil?
-      ((p = planting.finished_at - Date.current).to_i) <= 0 ? 0 : p.to_i
+      ((p = planting.finished_at - Date.current).to_i) <= 0 ? "0" : p.to_i.to_s
     elsif planting.planted_at.nil? || planting.days_before_maturity.nil?
       "unknown"
     else
-      ((p = (planting.planted_at + planting.days_before_maturity) - Date.current).to_i <= 0) ? 0 : p.to_i
+      ((p = (planting.planted_at + planting.days_before_maturity) - Date.current).to_i <= 0) ? "0" : p.to_i.to_s
     end
   end
 

spec/helpers/plantings_helper_spec.rb

@@ -21,13 +21,13 @@ describe PlantingsHelper do
         days_before_maturity: 17
       )
       result = helper.display_days_before_maturity(planting)
-      expect(result).to eq 17
+      expect(result).to eq "17"
     end
 
     it "handles completed plantings" do
       planting = FactoryGirl.build(:planting, finished: true)
       result = helper.display_days_before_maturity(planting)
-      expect(result).to eq 0
+      expect(result).to eq "0"
     end
 
     it "handles plantings that should have finished" do
@@ -35,10 +35,10 @@ describe PlantingsHelper do
         quantity: 5,
         planted_at: Date.new(0, 1, 1),
         finished_at: nil,
-        days_before_maturity: 17
+        days_before_maturity: "17"
       )
       result = helper.display_days_before_maturity(planting)
-      expect(result).to eq 0
+      expect(result).to eq "0"
     end
 
     it "handles nil d_b_m and nil finished_at" do
@@ -60,7 +60,7 @@ describe PlantingsHelper do
         days_before_maturity: nil
       )
       result = helper.display_days_before_maturity(planting)
-      expect(result).to eq 5
+      expect(result).to eq "5"
     end
   end