remove existing file from .gitignore
remove existing file from .gitignore

listing existing files in .gitignore has no effects
that are desirable

especially - modifications of tracked files listed in gitignore are not ignored

main effect is confusing people using code

fixes #660

StevenBlack/hosts,StevenBlack/hosts,borisschapira/hosts,gfyoung/hosts,gfyoung/hosts