Update windows README with package development notes

README.windows.md

@@ -63,7 +63,7 @@ Julia runs on Windows XP SP2 or later (including Windows Vista, Windows 7, and W
     Now `exit` the MSYS2 shell and restart it,  *even if you already restarted it above*. This is necessary in case the system upgrade updated the main MSYS2 libs. Reopen the MSYS2 shell and continue with:
 
     ```
-    pacman -S diffutils git m4 make patch tar
+    pacman -S diffutils git m4 make patch tar msys/openssh
 ```
 
   5. Configure your MSYS2 shell for convenience:
@@ -114,6 +114,8 @@ Julia runs on Windows XP SP2 or later (including Windows Vista, Windows 7, and W
     touch deps/pcre-8.31/checked  # This path will depend on the version of PCRE.
     make -j 4   # Adjust the number of cores (4) to match your build environment.
 ```
+6. Setup Package Development Environment
+  1. The `Pkg` module in Base provides many convenient tools for [developing and publishing packages](http://docs.julialang.org/en/latest/manual/packages/). One the packages added through pacman above was `openssh`, which will allow secure access to GitHub APIs. Follow GitHub's [guide](https://help.github.com/articles/generating-ssh-keys) to setting up generating SSH keys to ensure your local machine can communicate with GitHub effectively. 
 
 ## Building on Windows with MinGW-builds/MSYS