doc: more typo fixes from Lance Li in #565.

README.markdown

@@ -3895,14 +3895,14 @@ However, the optional `max_headers` function argument can be used to override th
 
 ```lua
 
- local args = ngx.req.get_headers(10)
+ local headers = ngx.req.get_headers(10)
 ```
 
 This argument can be set to zero to remove the limit and to process all request headers received:
 
 ```lua
 
- local args = ngx.req.get_headers(0)
+ local headers = ngx.req.get_headers(0)
 ```
 
 Removing the `max_headers` cap is strongly discouraged.

doc/HttpLuaModule.wiki

@@ -3226,13 +3226,13 @@ Note that a maximum of 100 request headers are parsed by default (including thos
 However, the optional <code>max_headers</code> function argument can be used to override this limit:
 
 <geshi lang="lua">
-    local args = ngx.req.get_headers(10)
+    local headers = ngx.req.get_headers(10)
 </geshi>
 
 This argument can be set to zero to remove the limit and to process all request headers received:
 
 <geshi lang="lua">
-    local args = ngx.req.get_headers(0)
+    local headers = ngx.req.get_headers(0)
 </geshi>
 
 Removing the <code>max_headers</code> cap is strongly discouraged.