format docstrings across lines

[drernie]

Right now it inserts "$$" instead of newlines.

.hc 0.5.3;
; ```
; This is test
; ```
# “$$This is test$$”

[drernie]

But the unit test works!?!

    it('joins multi-line doc-strings into strings', () => {
      const input = '```\nDoc String\n```'
      const result = evaluate(input)
      expect(result.toString()).to.equal('[“\nDoc String\n”]')
    })

Why doesn't the interpreter and the test doc?

[drernie]

Ah. Readline. Need to call evaluate Repeatedly.