Don't bother parsing or encoding selectors that are only used in HTML

[adamgian]

i.e. people doing this in their markup attributes to group/separate groups of classes:

<div class="[ foo  foo--bar ]  baz">

<div class="col m_4 t_6 d_8 / country-list / box box--rounded box--semi-transparent box--bottom-texture">

Square braces and the slashes are superficial here if they are not appearing anywhere else (e.g. stylesheets and js).

Would expect the above to be rewritten, for example, into:

<div class="[ a  b ]  c">

<div class="d e f g / h / i j k l">

[adamgian]

Tests are now up to date.