Allow homebrew to install tapped packages.

Homebrew has the concept of "taps": repositories with custom formulas.
These formulas live in /usr/local/Library/Taps, instead of the
usual /usr/local/Library/Formula.

This commit checks for the presence of tapped formulas, to allow for:

```ruby
  # Without this commit, babushka would be unable to find and install this package
  dep do "apple-gcc42", :template => "bin" do
    requires "homebrew-dupes.tap"
    installs "homebrew/dupes/apple-gcc42"
  end
```

Note taps still need to be installed before babushka will find
them:

```ruby
  dep "homebrew-dupes.tap" do
    requires "homebrew"

    TAPS_DIR = "/usr/local/Library/Taps"

    met? do
      "#{TAPS_DIR}/homebrew-dupes".p.exists?
    end

    meet do
      shell "mkdir -p #{TAPS_DIR}"
      log_shell "Brewing Homebrew Dupes tap", "homebrew tap
  homebrew/dupes"
    end
  end
```
Default to installing 'nodejs', which is what most pkg managers use.

I made this change to fix the dep for arch, which uses 'nodejs'. But most other systems (yum & gentoo among others) use 'nodejs' too. One exception is freebsd, which uses 'node' like brew; I've added a case for it here.
Require spec_helper to get the Fancypath specs running in isolation.
Add Fancypath#puts, with the same behaviour as IO#puts.
Pedantry: 'or' is correct here.
Merge branch 'homebrew-tapped-formulas'
Merge branch 'master' into ssh