add back some backtrader compat imports

Author: mrjbq7

CHANGELOG

@@ -7,6 +7,8 @@
 
 - [FIX]: Don't require pip, it's not needed
 
+- [FIX]: Add back some import compat for backtrader
+
 0.6.6
 =====
 

talib/abstract.py

@@ -2,6 +2,7 @@
 from ._ta_lib import Function as _Function, __TA_FUNCTION_NAMES__, _get_defaults_and_docs
 
 # add some backwards compat for backtrader
+from ._ta_lib import TA_FUNC_FLAGS, TA_INPUT_FLAGS, TA_OUTPUT_FLAGS
 
 _func_obj_mapping = {
     func_name: getattr(_ta_lib, func_name)