Update README.md

Author: amccaugh

README.md

@@ -19,7 +19,7 @@ GDS scripting that's intuitive, fast, and powerful.  For Python 2 and 3.
 - Install or upgrade with `pip install -U phidl`
 - Python 2 >=2.6 or Python 3 >=3.5
 - If you are on Windows or Mac and don't already have `gdspy` installed, you will need a C++ compiler
-    - For Windows + Python 3, install the Microsoft ["Build Tools for Visual Studio"](https://www.visualstudio.com/downloads/#build-tools-for-visual-studio-2017)
+    - For Windows + Python 3, install ["Build Tools for Visual Studio"](https://www.visualstudio.com/downloads/#build-tools-for-visual-studio-2017) (make sure to check the "C++ build tools" checkbox when installing)
     - For Windows + Python 2, install [Microsoft Visual C++ Compiler for Python 2.7](https://www.microsoft.com/en-us/download/details.aspx?id=44266)
     - For Mac, install "Xcode" from the App Store, then run the command `xcode-select --install` in the terminal