add big decimal conversion

add spec for big decimal conversion

lib/rails_param/param.rb

 module RailsParam
   module Param
 
+    DEFAULT_PRECISION = 14
+
     class InvalidParameterError < StandardError
       attr_accessor :param, :options
     end
@@ -54,6 +56,7 @@ module RailsParam
         return Array(param.split(options[:delimiter] || ",")) if type == Array
         return Hash[param.split(options[:delimiter] || ",").map{|c| c.split(options[:separator] || ":")}] if type == Hash
         return (/(false|f|no|n|0)$/i === param.to_s ? false : (/(true|t|yes|y|1)$/i === param.to_s ? true : nil)) if type == TrueClass || type == FalseClass || type == :boolean
+        return BigDecimal.new(param, (options[:precision] || DEFAULT_PRECISION)) if type == BigDecimal
         return nil
       rescue ArgumentError
         raise InvalidParameterError, "'#{param}' is not a valid #{type}"

spec/rails_param/param_spec.rb

@@ -100,6 +100,20 @@ describe RailsParam::Param do
         expect(controller.params["foo"]).to eql(DateTime.parse("2014-08-07T12:25:00.000+02:00"))
       end
 
+      describe "BigDecimals" do
+        it "converts to BigDecimal using default precision" do
+          allow(controller).to receive(:params).and_return({ "foo" => 12345.67890123456})
+          controller.param! :foo, BigDecimal
+          expect(controller.params["foo"]).to eql 12345.678901235
+        end
+
+        it "converts to BigDecimal using precision option" do
+          allow(controller).to receive(:params).and_return({ "foo" => 12345.6789 })
+          controller.param! :foo, BigDecimal, precision: 6
+          expect(controller.params["foo"]).to eql 12345.7
+        end
+      end
+
       describe "booleans" do
         it "converts 1/0" do
           allow(controller).to receive(:params).and_return({ "foo" => "1" })