Update barracuda dependency to 1.0.4 (#4644)

* update barracuda dep to 1.0.4

* changelog

* Update CHANGELOG.md

com.unity.ml-agents/CHANGELOG.md

 #### com.unity.ml-agents (C#)
 - Update documentation with recommended version of Python trainer. (#4535)
 - Log a warning if a version of the Python trainer is used that is newer than expected. (#4535)
+- Update Barracuda to 1.0.4. (#4644)
 
 ### Bug Fixes
 #### com.unity.ml-agents (C#)

com.unity.ml-agents/package.json

   "unity": "2018.4",
   "description": "Use state-of-the-art machine learning to create intelligent character behaviors in any Unity environment (games, robotics, film, etc.).",
   "dependencies": {
-    "com.unity.barracuda": "1.0.3",
+    "com.unity.barracuda": "1.0.4",
     "com.unity.modules.imageconversion": "1.0.0",
     "com.unity.modules.jsonserialize": "1.0.0",
     "com.unity.modules.physics": "1.0.0",