* Add relay operation relay.op.tan.
* Update tan implementation in TVM.
* Update tests.
* Add shape function for tan.
* Add missing main test to python/frontend/tensorflow/test_forward.
* Revert, back to sin/cos.
* Revert "Revert, back to sin/cos."
This reverts commit 4da5b503b921585ba9d80944b29136142b575c40.
* Fix implementation of tan in cuda. Do not support tan for float16.
Simplify topi/tests/python/test_topi_math. Add testing for tan with float32 and float64.
Finally implement tan as sin/cos in llvm.
