Remove extras from composer.json.

[ci skip]
Add more badges to README.
Removed hhvm from allow failures
Merge pull request #204 from GrahamCampbell/patch-1

Removed hhvm from allow failures
Apply workaround for bug in versions of PHP < 5.3.9.

This change is needed to address a bug in older versions of PHP 5.3
affecting inheritance (see https://bugs.php.net/bug.php?id=66818).
[phpdoc] Fix missing throws of phpdoc headers.
Change order of throws
Merge remote-tracking branch 'github/pr/208'

Conflicts:
	README.md
	composer.json
Add hhvm-nightly as a testing environment on Travis CI.