Only stop if the transition on this element ended

This way it doesn't end when some random element elsewhere on the page has an ending transition.

It must be noted that this is not a complete fix. If you have multiple transitions on the element, it still ends when the first ends.

I ran into this not working (the transition ends almost immediately, because some unrelated transition ends). This fixes it for me, but I was wondering whether this cornercase was considered, and whether the other cornercase (multiple transitions) was considered.

I think it's very hard to get this correct, and think it might be better to make the timeout explicit, or at least allow to set it explicit, and fall back to this behaviour. But I'm really interested in feedback on this one.
Added event parameter
Make sure it works when we have no css transitions
add picture element and related attributes
add picture to xjs.knownTags
Add support for <dialog> tag.

fixes #2017
use attribute for media, srcSet and sizes
Fix typo
Improve debugging for methods using ReactPerf
Combine displayName using underscore
Add newline before JSX spread when appropriate

Previously, we were losing the newline before a JSX spread attribute which would cause the lines to not match up; this fixes the problem.
SVG logo

I traced the current logo in Illustrator to get a good version. And with
SVG we don't need any 2x magic because it's already vector. I should
probably care about IE8, but I don't.
Add support for <dialog> tag's open attribute.
Small tweaks to HTML to JSX page:
 - Remove "Compiled JS" tab since it doesn't make sense
 - Relabelled editor to "Live HTML Editor" rather than "Live JSX Editor"
Fix DOMProperty bitmask checking
Merge pull request #2101 from jeffchan/patch-1

Fix typo in ReactDefaultPerfAnalysis comment
Merge pull request #2124 from Daniel15/htmltojsx-fixes

Small tweaks to HTML to JSX page
Merge pull request #2120 from zpao/svg-logo

[docs] SVG logo
Fix broken link in animation docs

Missed in #2068
Merge pull request #2033 from pekim/master

Add support for <dialog> tag.