Fix #266: Document further how 'text' vs. 'bytes' values are stored.

Note how the two differ in Python2 vs. Python3.

Fixes #266.
Not absolutely ([ReStructuredText directives](http://docutils.sourceforge.net/docs/ref/rst/restructuredtext.html#directives) require a blank line before the `block` if they have either `options` or `arguments`:  it is generally cleaner *always* to have the block start that way.