TODO

 1. [DONE] Fix 'mml$involves'

 2. [DONE] Fix 'mml$groups'

 3. [DONE]
    Add RE info

 4. [DONE] 
    Organize a list-form output object so the class can pick it up.

 5. [DONE] 
    Link the new names, make the class dump the list components required
    by Stan for r.e. specification. Also simplified the class s.t. it 
    has a single 'expose' method and does not track re's itself.

 6. [FUTURE]
    Formula parsing needs to extend to handle getting lables for complex
    random effects (e.g.- y ~ x + (a * b | d)) should parse out into
    three sets of RE's with independent variances.  For the moment those
    formulas can just be avoided.

 7. [FIXME] 
    This really needs formal tests.  These classes would be straightforward
    it's just the issue of coming up with some invariants and time.