Disable attribute validation by default

Add support for fredemmott/type-assert v1.0

Remove getWaitHandle()->join()

replaced with HH\Asio\join()

fixes hhvm#170. Tested with 3.15 and nightly

Change contenteditable and draggable from bool to enum { "true", "fal…

…se" }

fixes hhvm#155

Remove bogus assert

 - unneeded
 - typechecker and tests happy
 - needed for 3.12 as assert.active default has changed

Remove Travis-CI support

Version of HHVM too old :(

Merge pull request hhvm#148 from fredemmott/num-arraykey

Add support for num and arraykey attributes

Update README to prefer stable versions

refs hhvm#144

Render/process everythign recursively - turn XHP tree into an async tree

- all tests pass, including tests added that failed against previous PR
- every element renders itself and it's children
- all child rendering is async
- so, the XHP tree becomes a corresponding async tree

This means that asyncRender() at different depths in the tree can be executing simultaneously.

There shouldn't be much of a performance cost, as HHVM should convert things things
to a StaticWaitHandle when XHPAsync isn't being used.

fixes hhvm#136
fixes hhvm#85
fixes hhvm#139

Automatically call transferAttributes as needed.

- split out XHPBaseHTMLHelpers to just implement the ID and class helpers
  without transferAttributes
- added tests
- XHPHelpers should probably be renamed to XHPHTMLHelpers in XHP-Lib 3, and
  the bulk of the transfer/copyattribtues functiontionality split to
  XHPTransferAttributes or something like that. Keeping like this for now to
  reduce BC breakage
- Allows implementation of non-HTML helpers; until the above modification happens
  this will involve copypasta, but better than the current situation.
- I /think/ this gets rid of the render()/compose() pattern.

fixes hhvm#130
closes hhvm#133