bootstrap: put backup files in a subdirectory

Keep the noise of `*.bak` files out of the home directory by instead
moving backup targets into ~/.backups.

Don't be alarmed when you look into ~/.backups and see that it appears
empty; the original dot files are moved in there without being renamed,
so they're invisible unless you look at them with the appropriate flags
(eg. `ls -a`).

Signed-off-by: Wincent Colaiuta <win@wincent.com>
bootstrap: more concise output

For the old output, run as:

  DEBUG=1 ruby bootstrap.rb

Otherwise, enjoy the new, concise output.

Signed-off-by: Wincent Colaiuta <win@wincent.com>