Less whitespace
extract parse for reuse
Expressions and expressions in list.

I chose to make every code a list of expressions, i.e.
'abc' is not an atom, it's an expression list containing a
single atom. I tried making the grammar make the case of single
expressions fall through to their component but found it 
complicated the grammar past my understanding.

Schemer::Expressions could just be an array, but assuming I
will add more later.