Dot script changes (apache#159)

* Add get_synthetic_datasets

* Move to test_utils

* Remove _get_uniform_dataset

* Move validation to its own function

* Refactor the validation code for csr generation

* Make test_powerlaw a nested function

* Change SparseNDArray to CSRNDArray

* Refactoring changes to dot.py

* Fix mxnet test_utils changes

* Remove pdb statement

* Add distribution parameter

* Refactor benchmarking script

* Remove unused code

* Make style changes and remove unused code

* Change typo in comment

* Add transpose support

* Change typo

* 4 decimal points needed for density

* Add rsp support for real datasets

* Correct variable name mini_file_name

* Move wait_to_read outside if

* Seperate out scipy and mxnet logic in bench_dot

* Fix lhs_trans issue

* Move transpose outside measure_cost

* Compute transpose inside measure_cost

* Remove unused variables