1. use set_value() to set weight.
2. use weight in PositionEmbedding instead of protected member `_w`.
3. fix data layout for Embedding, the tailing sized-1 dimension is removed, update documentation, 
4. fix tensorboard tags, spaces are replaced with `_`.

test=develop

* ini commit for deepvoice, add tensorboard to requirements

* fix urls for code we adapted from

* fix makedirs for python2, fix README

* fix open with encoding for python2 compatability

* fix python2's str(), use encode for unicode, and str() for int

* fix python2 encoding issue, add model architecture and project structure for README

* add model structure, add explanation for hyperparameter priority order.

* fix repitiio n in README_cn, and reorder that in README

* README update; fix integer division issues for python2 compatability

* fix data type for input data, specifier the int type as np.int64 to be platform agnostic

* fix README for preprocess.py, use io.open instead of open for python2 compatability.

* update commanline options, use new save/load API

* fix IO conflict bug for data parallel training

* only construct summary writer in process 0 to further avoid conflict

* ini commit for deepvoice, add tensorboard to requirements

* fix urls for code we adapted from

* fix makedirs for python2, fix README

* fix open with encoding for python2 compatability

* fix python2's str(), use encode for unicode, and str() for int

* fix python2 encoding issue, add model architecture and project structure for README

* add model structure, add explanation for hyperparameter priority order.