Revert "Merge pull request #463 from Shopify/stricter-identifiers"

This reverts commit a056f6521c, reversing
changes made to 7843bcca8d.

lib/liquid/lexer.rb

@@ -9,11 +9,9 @@ module Liquid
       '['.freeze => :open_square,
       ']'.freeze => :close_square,
       '('.freeze => :open_round,
-      ')'.freeze => :close_round,
-      '?'.freeze => :question,
-      '-'.freeze => :dash
+      ')'.freeze => :close_round
     }
-    IDENTIFIER = /\w+/
+    IDENTIFIER = /[\w\-?!]+/
     SINGLE_STRING_LITERAL = /'[^\']*'/
     DOUBLE_STRING_LITERAL = /"[^\"]*"/
     NUMBER_LITERAL = /-?\d+(\.\d+)?/

lib/liquid/parser.rb

@@ -75,13 +75,6 @@ module Liquid
 
     def variable_signature
       str = consume(:id)
-      while consume?(:dash)
-        str << "-".freeze
-        str << consume(:id)
-      end
-      if consume?(:question)
-        str << "?".freeze
-      end
       if look(:open_square)
         str << consume
         str << expression