Add nested blocks Handlebars test

This test is broken in Handlebars@1.0.0-rc.3 because of a regression,
but that regression is fixed in Handlebars@v1.0.10.
Update Handlebars importing script and wrappers

This updates the scripts which import Handlebars and the YUI wrappers to
prepare for importing Handlebars@v1.0.10.
Import Handlebars @ v1.0.10

Updates Handlebars to the latest published [to npm] version.

**Note:** `Handlebars.VERSION` still reports "1.0.0-rc.3".
Update Handlebars change history
Fix a confusing typo in the Template user guide. Fixes #543
Merge branch 'live-docs' into dev-master
Replace political sample text with something a little less divisive.

I still feel really uncomfortable with how much of this example is lifted
straight from the Boston Globe (especially the hot-linked images), but I
don't have time to fix everything right now.
Merge branch 'live-docs' into dev-master
Merge branch 'handlebars-v1.0.10' into dev-master
Build Handlebars @ v1.0.10