Handle installation for 'fish' shell (#690)
Handle installation for 'fish' shell (#690)

* Handle installation for 'fish' shell

'fish' is a popular shell. This commit adds support for proper detection and installation of yarn in 'fish' shell. If the detected shell is 'fish', add path to ~/.yarn/bin in $HOME/.config/fish/config.fish file.

* Use a more modern way of setting $PATH in fish

Set `~/.yarn/bin` in `$fish_user_paths` instead of setting it in `~/.config/fish/config.fish` file.

See [suggestion from fish documentation](https://github.com/fish-shell/fish-shell/issues/527#issuecomment-13811988) for more reference.

* Run command to set $fish_user_paths instead of evaluating a string.

MiguelAlho/yarn,onemen/yarn,joeyespo/yarn,suitupalex/yarn,mvestergaard/yarn,dxu/yarn,onemen/yarn,kasperlewau/yarn,andreypopp/esy,mgcrea/yarn,dguo/yarn,bsansouci/esy,bsansouci/esy,suitupalex/yarn,FLGMwt/yarn,bsansouci/esy,ConAntonakos/yarn,FLGMwt/yarn,kasperlewau/yarn,mourner/yarn,dxu/yarn,lawliet89/yarn,ConAntonakos/yarn,troydemonbreun/yarn,mourner/yarn,joeyespo/yarn,andreypopp/esy,CHECK24/yarn,andreypopp/esy,seripap/emojiless-yarn,seripap/emojiless-yarn,mvestergaard/yarn,mgcrea/yarn,lawliet89/yarn,MiguelAlho/yarn,dguo/yarn,troydemonbreun/yarn,CHECK24/yarn