Generate new hash using html5 block names
Add a few more html5 blocks
Add file used to generate html_blocks.h
Merge branch 'master' into html5
Add tests
Add changelog entry
Merge branch 'master' into html5

Conflicts:
	CHANGELOG.md
Remove source file for html_blocks.h
Remove tests from specs. Change to Ruby tests
add indefinite article and update year
Merge pull request #409 from caleorourke/patch-1

add indefinite article and update year [ci skip]
Merge pull request #331 from silverhammermba/html5

Recognize HTML5 Block-Level Elements
Add a `Safe` renderer to deal with users' input

Since we can't turn on security options by default for the sake of
backward compatibility, let's provide a new renderer object that will
make it easy to deal with, for instance, users' input.

The `safe_links_only` and `escape_html` options are turned on by default
but you can still override them if you prefer `filter_html` for example.

The `block_code` callback doesn't output any class attribute as this can
be unsafe since we can specify existing classes as the language.

Fixes #375 and #384.