refactor(e): improve codie security

* Use -w flag to test writability
* Use 'sudo -e --' to:
    * -e: protect against security issues ;
    * --: filename starting with '-'.

See blog for explanations: http://blog.edouard-lopez.com/reduce-frictions-and-cognitive-load-when-editing-files/
fix(merc,md): unalias existing/conflicting alias
feat(bashrc): add correction in directories name
feat(bashrc): add sudo completion
feat(merc): add an alert() to send notify to desktop
feat(tmux): get notification there is inside other windows

This appear in the form of a notification line at the bottom on tmux
docs(tmux): add shortcut infos
feat(tmux): configure Alt+arrows to navigate panes
fix(tmux): enable Ctrl+arrow to navigate words
feat(alias): add alias for SSH access (KISS)