.bash_prompt: Interpret escape sequences correctly in all cases

Closes #407.
.vimrc: Avoid creating backups when editing files in `/tmp`

See http://vim.wikia.com/wiki/Editing_crontab.
.aliases: Remove the now-broken `whois` alias

Closes #397.
Merge branch 'master' of https://github.com/mathiasbynens/dotfiles

# By Mathias Bynens (2) and April Arcus (1)
# Via Mathias Bynens
* 'master' of https://github.com/mathiasbynens/dotfiles:
  .aliases: Remove the now-broken `whois` alias
  .vimrc: Avoid creating backups when editing files in `/tmp`
  .bash_prompt: Interpret escape sequences correctly in all cases