* Use last k observations instead of last k epochs.

* rewriting in a more concise way

* Fix valid_for_nccl: nccl supports fp16 now

* Check TF version first for valid_for_nccl

update docs

update docs

* start the showcase of exporting models from tensorpack

* mobile support

* showcase loading a frozen and pruned graph

* fix travis issues

* add docs

* add example image

* classes to functions

* typo

* typos

* some more fixes

* update docs

* rename the example

* make the pix2pix support multi gpu trainning

* Update Image2Image.py

* Update Image2Image.py

* Update Image2Image.py