Prepare 0.1.7 release.

Remove codecov badge

removing tf.keras dependency (#771)

* removing tf.keras dependency

* removing tf.keras dependency

* removing tf.keras dependency

* removing tf.keras dependency

Added some docstrings ops/nn.py (#677)

* Small typo

* Added some docstrings

* Remove extra lines

* Unindent examples // use floats in example section

Add docstrings in numpy (#617)

* Add docstrings in numpy

* passed review comments

Upgrade version number.

add adadelta for torch (#534)

Co-authored-by: Haifeng Jin <haifeng-jin@users.noreply.github.com>

Prepare version string for release.