Vim: update plugins in ~/.janus to latest versions
Bash: enable npm's built-in completion

This is in addition to our own npm path additions (wherein we add the
`node_modules/.bin/` directory of the module for the current directory
[should one exist] to our `$PATH`). The completions described by this
commit is simply Bash completion of npm sub-commands.
Bash: update npm bin directory `$PATH` updater code

In .bash_profile, in the add_npm_to_path() function we call as part of
`$PROMPT_COMMAND`, we use the `npm bin` command to find the current
`.bin` directory, rather than calling `npm root` and adding `/.bin` to
that path. This should be more robust and accurate.
Bash: on Mac, alias `b` to `brew`
Merge commit 'be793c2b2ad38dbe92e99026ec4964aceb499dd4'