* Added elu operator to Python API.

* Added missing file.

* Specified elu function description.

* Expand docstring

* [Py] Added test with scalar for elu operator.

* Bugfix

*  [Py] Changed input type in elu test.

* Update test_ops_binary.py

* [Py] Syntax bugfix.

* [Py] Added elu operator to list in documentation.