Update readme.md
Update readme.md

Bunch of small teaks:
* re-order screenshots
* capitalized some section sentence starting words
* made Mac help wanted more prominent
* Moved quick setup (TL;DR) section up
* Various misc readability and condensing tweaks
ryanoasis/vim-webdevicons,bronzdoc/vim-devicons,delphinus35/vim-devicons,ryanoasis/vim-devicons,lerrua/vim-devicons