Use block helpers in attributes again in accounts-ui

Now that it's once again supported
Fix most of accounts-ui-viewer
Support 'class' attributes on SVG elements
Merge branch 'devel' into shark
Fix 'class' attribute on SVG elements
Fix 'class' attribute on SVG elements, take 2
dedup test names
Remove outdated comment
Make wordplay example not depend on String.trim

Not present in IE 8
Make htmljs Tag constructor IE 8 safe

To make tags print nicely in the console, we dynamically create constructor functions of the form `function DIV() { ... }`, which is still the only thing Chrome responds to.  Modern browsers interpret a function expression of this form as exposing a symbol `DIV` only to lexical scope of the *body* of the function.  IE 8 does something else -- I forget what exactly, but it's not good.  Also I think `new Function("... code ...")` captures scope in IE 8, so we need to be careful what sort of names we inject.
More wordplay IE 8 fixes
Don't depend on data context in emboxed constant
Tests for emboxValue / _isEmboxedConstant
Fix bug in parsing of HTML attributes

e.g. <foo bar baz>.  (D'oh.)
Merge remote-tracking branch 'origin/devel' into shark

Conflicts:
	packages/handlebars/.npm/package/npm-shrinkwrap.json
Merge remote-tracking branch 'origin/devel' into shark
Add tests (mainly failing) for #markdown
Attributes of the type 'xlink:something', used in SVG, should be set using the correct namespace in order to work
start of htmljs README
further internal docs and cleanup