message: Add complex support for tan
  At the moment tan in tensorflow supports float and double, but
  not complex types.
  This fix adds the support for tan, and removes related TODO in
  the test
diff: @@ -16,7 +16,7 @@ limitations under the License.
  #include "tensorflow/core/kernels/cwise_ops_common.h"
  namespace tensorflow {
  -REGISTER2(UnaryOp, CPU, "Tan", functor::tan, float, double);
  +REGISTER4(UnaryOp, CPU, "Tan", functor::tan, float, double, complex64, complex128);
  #if GOOGLE_CUDA
  REGISTER2(UnaryOp, GPU, "Tan", functor::tan, float, double);
  