Fix filter parser regex for filter args without separating spaces.

The regex was using \S+ to match the comma between the filters
arguments, but would continue to match idependent quote characters and
filter separators. This can result in multiple filters being interpreted as
a single one with many arguments.

lib/liquid/variable.rb

@@ -11,7 +11,7 @@ module Liquid
   #   {{ user | link }}
   #
   class Variable
-    FilterParser = /(?:#{FilterSeparator}|(?:\s*(?!(?:#{FilterSeparator}))(?:#{QuotedFragment}|\S+)\s*)+)/o
+    FilterParser = /(?:#{FilterSeparator}|(?:\s*(?:#{QuotedFragment}|#{ArgumentSeparator})\s*)+)/o
     attr_accessor :filters, :name
 
     def initialize(markup)

test/liquid/variable_test.rb

@@ -66,6 +66,10 @@ class VariableTest < Test::Unit::TestCase
     var = Variable.new('hello|textileze|paragraph')
     assert_equal 'hello', var.name
     assert_equal [[:textileze,[]], [:paragraph,[]]], var.filters
+
+    var = Variable.new("hello|replace:'foo','bar'|textileze")
+    assert_equal 'hello', var.name
+    assert_equal [[:replace, ["'foo'", "'bar'"]], [:textileze, []]], var.filters
   end
 
   def test_symbol