[PASS] Use likely tag & enable LoopPartition by default (#132)

* [PASS] Use likely tag & enable LoopPartition by default

* [PASS] Support thread_axis partition

* Take IfThenElse branch method

* [PASS] Insert branch at the innermost thread scope

* [PASS] Select candidates before trying to partition & add test for select

* [PASS] Clean code

* Fix

* Remove print & assert vectorize happens