Fix issue #475: diet doesn't allow boolean attributes without value in HTML5
Add html shortcut as HTML5 doctype
Use OutputContext instead for m_isHTML5 flag
Handle Diet includes as separate mixins().

This commit prepares for support of string templates, originally proposed by Stefan Koch (Uplink_Coder) in #482.
Implement string includes for Diet templates. See #482.
Redo pull #516 without compiler errors (dietStringParser signature improvement).

Fixes #516.
Name Diet string includes like their string expression.
Merge pull request #512 from nazriel/issue475

Fix issue #475: diet doesn't allow boolean attributes without value in H...
Fix issue #372: Don't print `class` attribute with empty value for Diet template
Merge pull request #519 from nazriel/issue372

Fix issue #372: Don't print `class` attribute with empty value for Diet ...
Fix issue #520: Allow null to be used to omit Diet template attributes
Update app.d

nicer way to write duration in seconds (just warming up with this module, cause i need to use it now ^^)
Merge pull request #522 from Extrawurst/patch-3

Update app.d
Fix HTTP client in conjunction with non-SSL connections (null pointer dereference). Fixes #523.
Add initial support for Redis Pub/Sub.
Revise Redis Pub/Sub method signatures and implement the callback mechanism.
Redis Publish takes string arguments only.
Move Redis subscription listening code to RedisSubscriber.
Make RedisSubscriber.listen() asynchronous.
Add Redis Pub/Sub async subscribe/unsubscribe support.