solved gflags import problem

[pocandraspoc]

gflags are not supported any more
import gflags as flags
better to use absl instad

chris-chris/pysc2-examples#5 (comment)

[H-Park]

This issue is more widespread in this project than just one file.

Files that have from pysc2.lib import app and import gflags as flags

preprocess/preprocess.py
parse_replay/extract_actions.py
parse_replay/parse_replay.py
parse_replay/replay2global_features.py
parse_replay/sample_actions.py
extract_features/global_feature_vector
extract_features/replay_stat.py
extract_features/spatial_feature_tensor.py

@wuhuikai @pocandraspoc