Merge pull request #2 from waissbluth/fix-bucket-size

Fix bucket size calculation

lib/pg_histogram/histogram.rb

@@ -19,7 +19,7 @@ def initialize(query, column_name, options = {})
           @min = options[:min] || 0
           @max = options[:max]
           @buckets = options[:buckets]
-          @bucket_size = calculate_bucket_size
+          @bucket_size = (@max - @min).to_f / @buckets
         else
           @min = options[:min]
           @max = options[:max]
@@ -60,10 +60,6 @@ def source_max
       @source_max ||= subquery.maximum(pure_column(true))
     end
 
-    def calculate_bucket_size
-      (source_max - source_min).to_f / @buckets
-    end
-
     def num_buckets
       @buckets ||= ((max - min) / bucket_size).to_i
     end