Add a replay toolkit

[Yancey1989]

To make profiling a single cluster easier, we should implement a toolkit to replay a cluster. For my preliminary idea, this toolkit includes two phases:

1. dump cluster args and compiler input IR with the protobuf format on disc_launch_op, users can specify the iteration with environ variable and then find the dump message on logs as the following example:

   Launch the training jobs with some environment variables:

   export BLADEDISC_REPLAY_ITERATION=1000
   export BLADEDISC_REPLAY_CLUSTER=cluster_24
   python train.py > train.log
   ...

   Then users can find the replay logs with grep command after period of time:

   grep "BladeDISC replay toolkit" train.log
   BladeDISC replay toolkit  dumps the disc compiler input file : `/tmp/tempfile-xxxx.input`, record args file: 
   `/tmp/record_args.xxx.pb`

2. execute with an executable program disc_replay_main with the nvprof profiler toolkit

   nvprof disc_replay_main /tmp/tempfile-xxxx.input /tmp/record_args.xxx.pb

TODOs:

• implement disc_replay_main executable program.
• dump record args on tensorflow bridge site.

[Yancey1989]

#84 implements this feature, so I will close this issue.