Merge pull request #89 from tokyorubykaigi12/fix-sold-out

Plan#sold_out?: Properly respect Plan capacity

Author: sorah

app/models/plan.rb

@@ -15,7 +15,7 @@ def available?(t = Time.zone.now)
   end
 
   def sold_out?
-    !capacity || sponsorships.active.count > capacity
+    !capacity || sponsorships.active.count >= capacity
   end
 
   def closed?(t = Time.zone.now)