Release 0.5.1 (#531)

* Add docstring correlation cost (#514)

* Add Docstring CorrelationCost
* Add CorrelationCost Documentation
* Small reformat

* BLD: built on 2.0.0-rc1

* DOC: doc for 0.5.1

* Fix optical_flow test case (#527)

* typo fix (#523)

* CLN: fix file permission 755 in #527

* CLN: use public api, tf.keras

Author: facaiy

build_deps/requirements.txt

@@ -1,2 +1,2 @@
 # TensorFlow greater than this date is manylinux2010 compliant
-tensorflow==2.0.0-rc0
+tensorflow==2.0.0-rc1

build_deps/requirements_gpu.txt

@@ -1,2 +1,2 @@
 # TensorFlow greater than this date is manylinux2010 compliant
-tensorflow-gpu==2.0.0-rc0
+tensorflow-gpu==2.0.0-rc1