Fixed OpenURL urls

- Ensured consistency of how (Experimental) appears in docs.

README.md

 * Built-in support for Imitation Learning
 * Flexible Agent control with On Demand Decision Making
 * Visualizing network outputs within the environment
-* Simplified set-up with Docker _(Experimental)_
+* Simplified set-up with Docker (Experimental)
 
 ## Documentation and References
 

docs/Getting-Started-with-Balance-Ball.md

 
 ![Example TensorBoard Run](images/mlagents-TensorBoard.png)
 
-## Embedding the Trained Brain into the Unity Environment _[Experimental]_
+## Embedding the Trained Brain into the Unity Environment (Experimental)
 
 Once the training process completes, and the training process saves the model 
 (denoted by the `Saved Model` message) you can add it to the Unity project and 

docs/Using-TensorFlow-Sharp-in-Unity.md

-# Using TensorFlowSharp in Unity _[Experimental]_
+# Using TensorFlowSharp in Unity (Experimental)
 
 ML-Agents allows you to use pre-trained [TensorFlow graphs](https://www.tensorflow.org/programmers_guide/graphs) inside your Unity games. This support is possible thanks to [the TensorFlowSharp project](https://github.com/migueldeicaza/TensorFlowSharp). The primary purpose for this support is to use the TensorFlow models produced by the ML-Agents own training programs, but a side benefit is that you can use any TensorFlow model.
 

unity-environment/Assets/ML-Agents/Scripts/Agent.cs

 /// see the Examples/ directory within this Unity project.
 /// </remarks>
 [HelpURL("https://github.com/Unity-Technologies/ml-agents/blob/master/" +
-         "docs/Learning-Environment-Design-Agent.md")]
+         "docs/Learning-Environment-Design-Agents.md")]
 [System.Serializable]
 public abstract class Agent : MonoBehaviour
 {

unity-environment/Assets/ML-Agents/Scripts/Brain.cs

     /**< \brief Defines if the state is discrete or continuous */
 }
 
-[HelpURL("https://github.com/Unity-Technologies/ml-agents/blob/master/docs/Agents-Editor-Interface.md#brain")]
+[HelpURL("https://github.com/Unity-Technologies/ml-agents/blob/master/" +
+         "docs/Learning-Environment-Design-Brains.md")]
 /**
  * Contains all high-level Brain logic. 
  * Add this component to an empty GameObject in your scene and drag this 

unity-environment/Assets/ML-Agents/Scripts/CoreBrainInternal.cs

             "order to use the internal brain.", MessageType.Error);
         if (GUILayout.Button("Show me how"))
         {
-            Application.OpenURL("https://github.com/Unity-Technologies/ml-agents/blob/master/docs/Getting-Started-with-Balance-Ball.md#setting-up-tensorflowsharp-support");
+            Application.OpenURL("https://github.com/Unity-Technologies/ml-agents/blob/master/docs/Getting-Started-with-Balance-Ball.md#embedding-the-trained-brain-into-the-unity-environment-experimental");
         }
 #endif
     }