Revert back to barracuda 0.3.2-preview. (#3300)

com.unity.ml-agents/Editor/Unity.ML-Agents.Editor.asmdef

 {
     "name": "Unity.ML-Agents.Editor",
     "references": [
-        "Unity.ML-Agents",
-        "Barracuda"
+        "Unity.ML-Agents"
     ],
     "includePlatforms": [
         "Editor"

com.unity.ml-agents/Runtime/Unity.ML-Agents.asmdef

 {
     "name": "Unity.ML-Agents",
     "references": [
-        "Barracuda"
     ],
     "includePlatforms": [],
     "excludePlatforms": [],

com.unity.ml-agents/Tests/Editor/Unity.ML-Agents.Editor.Tests.asmdef

     "name": "Unity.ML-Agents.Editor.Tests",
     "references": [
         "Unity.ML-Agents.Editor",
-        "Unity.ML-Agents",
-        "Barracuda"
+        "Unity.ML-Agents"
     ],
     "optionalUnityReferences": [
         "TestAssemblies"
     "precompiledReferences": [
         "System.IO.Abstractions.dll",
         "System.IO.Abstractions.TestingHelpers.dll",
-        "Google.Protobuf.dll"
+        "Google.Protobuf.dll",
+        "Barracuda.dll"
     ],
     "autoReferenced": false,
     "defineConstraints": [

com.unity.ml-agents/Tests/Runtime/Unity.ML-Agents.Tests.asmdef

 {
     "name": "Unity.ML-Agents.Tests",
     "references": [
-        "Unity.ML-Agents",
-        "Barracuda"
+        "Unity.ML-Agents"
     ],
     "optionalUnityReferences": [
         "TestAssemblies"

com.unity.ml-agents/package.json

 	"unity": "2018.4",
 	"description": "Add interactivity to your game with ML-Agents trained using Deep Reinforcement Learning. \n\nFor best results, use this text to summarize: \n\u25AA What the package does \n\u25AA How it can benefit the user \n\nNote: Special formatting characters are supported, including line breaks ('\\n') and bullets ('\\u25AA').",
 	"dependencies": {
-		"com.unity.barracuda": "0.4.0-preview"
+		"com.unity.barracuda": "0.3.2-preview"
 	}
 }