Update directory path and update bashrc file (#4977)

* Update directory path 

- Update directory path with Tensorflow directoy folder: tensorflow/models/research/
- Add option to refresh source ~/.bashrc

* Update installation.md

research/object_detection/g3doc/installation.md

@@ -77,7 +77,7 @@ cp -r pycocotools <path_to_tensorflow>/models/research/
 The Tensorflow Object Detection API uses Protobufs to configure model and
 training parameters. Before the framework can be used, the Protobuf libraries
 must be compiled. This should be done by running the following command from
-the tensorflow/models/research/ directory:
+the [tensorflow/models/research/](https://github.com/tensorflow/models/tree/master/research/) directory:
 
 
 ``` bash
@@ -140,7 +140,11 @@ export PYTHONPATH=$PYTHONPATH:`pwd`:`pwd`/slim
 Note: This command needs to run from every new terminal you start. If you wish
 to avoid running this manually, you can add it as a new line to the end of your
 ~/.bashrc file, replacing \`pwd\` with the absolute path of
-tensorflow/models/research on your system.
+tensorflow/models/research on your system. After updating ~/.bashrc file you can run the following command:
+
+``` bash
+source ~/.bashrc
+```
 
 # Testing the Installation