Merge branch 'patch146'
Merge remote-tracking branch 'upstream/master' from simplepie/simplepie
Fix for Issue #327 - Purges MySql cache contents older than a configured value
Update Item.php

add support
http://www.rssboard.org/media-rss#media-thumbnails
use hash over title, content and link if guid not given
use serialized data for hashing
code cleanup
fix query to use prepared statements
[FreshRSS] New function add_attributes()

Just like there is a strip_attributes() function, here is a new
add_attributes() which works the same way, except it is to add
attributes instead of removing them.

Just like strip attributes(), add_attributes() comes with some default
settings, namely to add a few HTML5 attributes:
```html
<audio preload="none" />
<video preload="none" />
<iframe sandbox="allow-scripts allow-same-origin" />
```

Watch out that I have changed the signature of the protected functions
strip_tag() and strip_attr() for performance reasons (to avoid a loop of
new DOMXPath()). If this is a problem, I could propose a patch with the
old signatures.

This is a first attempt to report upstream some improvements made for
the FreshRSS news reader http://freshrss.org. If there is interest,
there will be more.
remove php notice when a date starts with '('
Added PHP 5.6, 5.5 and HHVM to travis.yml
Merge branch 'patch-1' of https://github.com/Nyholm/simplepie
Merge branch 'master' of https://github.com/blat/simplepie
Merge branch 'add_attributes' of https://github.com/Alkarex/simplepie
Merge branch 'master' of https://github.com/Raydiation/simplepie
Merge branch 'patch-1' of https://github.com/empiricompany/simplepie
Merge branch 'purge' of https://github.com/rapid2k1/simplepie