Fix bad range parsing.

lib/liquid/lexer.rb

@@ -15,6 +15,7 @@ module Liquid
     SINGLE_STRING_LITERAL = /'[^\']*'/
     DOUBLE_STRING_LITERAL = /"[^\"]*"/
     NUMBER_LITERAL = /-?\d+(\.\d+)?/
+    DOTDOT = /\.\./
     COMPARISON_OPERATOR = /==|!=|<>|<=?|>=?|contains/
 
     def initialize(input)
@@ -32,6 +33,7 @@ module Liquid
         when t = @ss.scan(DOUBLE_STRING_LITERAL) then [:string, t]
         when t = @ss.scan(NUMBER_LITERAL) then [:number, t]
         when t = @ss.scan(IDENTIFIER) then [:id, t]
+        when t = @ss.scan(DOTDOT) then [:dotdot, t]
         else
           c = @ss.getch
           if s = SPECIALS[c]

lib/liquid/parser.rb

@@ -53,8 +53,7 @@ module Liquid
       elsif token.first == :open_round
         consume
         first = expression
-        consume(:dot)
-        consume(:dot)
+        consume(:dotdot)
         last = expression
         consume(:close_round)
         "(#{first}..#{last})"