[Vim] Improve Dash maps

Another good opportunity for progressive enhancement of a built-in
command.
[Vim] Highlight some mixed indentation

The highlighting definitely errs on the cautious side.
[Vim] Do not include EOL in 'listchars'

Part of an experiment with having 'list' always set.
[Vim] Revert tiny style change in vimrc

Apparently, we shouldn't do that.

This reverts commit 5f44ab2cd014886f908160cfe0f404912168866b.
[Vim] Rearrange some settings

Fixes minor issue when sourcing vimrc, works with Neovim, better
organization.
[Vim] Revert "Don't let targets.vim clobber ia/aa & ir/ar"

This reverts commit 7457a2a3f98aa8fe5d648836f90bdb3c7380053d.

Targets.vim changed the defaults.
[Fish] Update Boxen script

Decided it's easier to just manually update it.
[General] Remove Rakefile

The responsibility of linking files into the home directory has been
shifted over to Boxen.