- Fixed all test cases to use using(Buffer)
- Fixed all test cases to explicitly specify session

Relative unit test in `OperationTest`.

Relative unit test in `OperationTest`.

Relative unit test in `OperationTest`.

Relative unit test in `OperationTest`.

* Add missing `operator >=`s

Also unit testing the new operators.

* Add missing `operator <=`s

Also unit testing all the operator cases.

* Add missing `operator >`s

Also unit testing all the operator cases.

* Add missing `operator <`s

Also unit testing the new operators.

Also unit testing the new operators.

Unit testing the operation too.

Exposing also the `IsFinite` one.
Unit testing both operations.

* removing unused namespaces

* implementing Tensor to scalar and scalar to tensor conversions

Also unit testing all the operator cases.

Also unit testing all the operator cases.

add RuntimeError exception class.
add meta_graph related classes.