added "with context" or "without context" import/include modifiers

--HG--
branch : trunk
diff --git a/jinja2/lexer.py b/jinja2/lexer.py
index ade9f92..3b65b95 100644
--- a/jinja2/lexer.py
+++ b/jinja2/lexer.py
@@ -218,7 +218,7 @@
         self.current = old_token
         return result
 
-    def skip(self, n):
+    def skip(self, n=1):
         """Got n tokens ahead."""
         for x in xrange(n):
             self.next()