#108 Copy when not editable + autocompletion for fish + #128 Search

In response to #108 I have made change to ask for the user if he want to copy the sheet to his DEFALT_CHEAT_DIR when the sheet is not editable.
Also added error message when couldn't create a new cheat telling the user to use sudo.

Also :
Just switching from bash to a more friendly interactive shell (fish) so I just made the autocomplete script.
So here is my contribution :)