Update README.md

Added double quotes to pip install; it did not work for me locally without the quotes

Author: vbrodsky

README.md

@@ -54,7 +54,7 @@ pip3 install -r requirements.txt
 To install dependencies required for data processing modules use:
 
 ```
-pip install labelbox[data]
+pip install "labelbox[data]"
 ```
 
 ## Documentation