Change Unit.multiplier type from decimal to float

Remove remnants related to BigDecimal.

lib/core_ext/range.rb

@@ -0,0 +1,31 @@
+class Range
+  # TODO: cleanup comments after commit
+  # * < nil, true < false
+  #if a.end == b.end
+  #  a.exclude_end? ^ b.exclude_end? ? (a.exclude_end? ? -1 : 1) : 0
+  #else
+  #  a.end <=> b.end || (a.end.nil? ? 1 : -1)
+  #end
+  #a.end == b.end ? (b.exclude_end? ? b : a) : [a, b].to_h.except(nil).min
+  #*(l[0] == r[0] ? (r[1] ? r : l) : [l, r].reject{ |e| e[0].nil? }.min)
+  def &(other)
+    case other
+    when Range
+      return nil unless self.overlap?(other)
+
+      both = [self, other]
+      return Range.new(
+        both.map(&:begin).compact.max,
+        *if self.end == other.end
+           other.exclude_end? ? [other] : [self]
+        else
+          both.select(&:end)
+        end.map { |r| [r.end, r.exclude_end?] }.min
+      )
+    when Array
+      return other.map { |o| self & o }.compact
+    else
+      return self.member?(other) ? other : nil
+    end
+  end
+end