reduce regexp searched text, since this usally occurs at the beginning for the file

__init__.py

@@ -44,7 +44,7 @@ UNICODE_POLICY = 'strict'
 
 CHARSET_DECL_RGX = re.compile('(?:charset|(?:(?:en)?coding))[=:\s"\']*([^\s"\']*)',
                               re.I | re.S | re.U)
-CHARSET_DECL_SEARCH_SIZE = 1024
+CHARSET_DECL_SEARCH_SIZE = 512
 
 CHARDET_MIN_SIZE = 20
 CHARDET_CONFIDENCE_THRESHOLD = 0.75