new zsh widgets

+ new fzf-cd-widget for running cd

* fzf-file-widget now properly escapes the special characters and supports
  multi-selection

* fzf-history-widget replaces the current line instead of appending to it
zsh widget fix

* fzf-cd-widget properly escapes the special characters
Merge pull request #5 from Vifon/zsh-widgets

new zsh widgets