Cleanup comments; Thanks Oleg! Closes #1

Feedback from Oleg:

Your implementation of align and nest seems corrects to me. Indeed all
margin control directives should translate to Stream elements of zero
width. Most of the pretty-printer merely pass those elements along. Only
the final stage, the formatter, heeds those directives. The formatter's
state will include left and right margins (or tab stops), adjusted upon
receiving the alignment directives. When breaking a line, the formatter
emits enough spaces or tabs to fill the left margin. So long as the
indenting directives never indent beyond the page width (which the
formatter can check and prevent), the width estimating remains sound. If
margins are modified, the effective page width will be less than w.
Therefore, if a group is found to have the width :too-far (greater than
w), it will certainly remain :too-far for the effective margins. Thus,
as you have already observed paying no attention to :align and other
margin directives in annotate-begins does work. It is actually correct.