Add Windows instructions

[bergren2]

Instructions here: https://github.com/junegunn/vim-plug

This is also useful in tandem with Visual Studio VsVim.

[bergren2]

Not sure what (if possible, any) packages need to be installed with something like Chocolatey.

[bergren2]

Ruby and Python definitely need to be installed.

[bergren2]

On Windows, convention is to use _vimrc etc, as well as keep files in vimfiles instead of .vim.

[bergren2]

Add Tomorrow theme: https://devblogs.microsoft.com/visualstudio/theming-in-visual-studio-just-got-a-lot-easier/

[bergren2]

Running into an issue with getting Python working for UltiSnips and Ctrl+P.