Add Note to requirements for Windows

[heri16]

Should indicate more clearly which component of Visual Studio Community Edition needs to be installed.

[riverrun]

I don't use Visual Studio, so I'm going to need your help to do that :)
I know that you need to install the C/C++ module / component separately now. Is there anything else that needs to be installed?

[dylantf]

I just installed it all from scratch on Windows 10, the process is the same.

• Install VS (Community Ed. is fine)
• Go to File > New > Project
• Choose C++, it will prompt to install the module. Close VS
• Go to search > "Developer Command Prompt for VS2015"
• cd to the VC directory, run vcvarsall.bat amd64 -- this must be run every time you try to compile comeonin
• cd over to your project, mix deps.get, mix deps.compile

[riverrun]

Great! I'll add this info to the wiki.
Thanks for your help.