Fix bug with switching to 'night' theme

When switching to 'night' theme, the first slide was shown
instead of correctly linking to the Themes slide.

Document vertical centering breaking backcompat

Essentially, slides have variable height now. This is not normally visible, but with transitions that have a non-transparent background, like `cube` or `page`, it is:




http://lab.hakim.se/reveal-js/?transition=cube




Before, slides had a fixed height, which means that presentations designed with that assumption in mind will look very different now.




Another aspect that I bumped into is that I used the slide's height to dynamically size images to fill the remainder of the space from the heading to the footer, like this (stripped to the essence):




          bigImage.style.height = section.offsetHeight - bigImage.offsetTop + 'px';




Alternatively, is there an easy way to restore the previous functionality?

Was at ~0.3.2, but doesn't seem to have been released properly.

Authors might want to use a shared reveal.js installation for all their
presentations such as:

	$ ls -1 -F
	20120105-how-to-use-git.html
	20121101-wikimedia-scaling.html
	reveal.js/
	$

In this case, the plugin callbacks will not be called at all.

When using head.js, the callback is marked as depending upon the loading of a
Javscript filename. The regex used to find out the filename is applied to the
full path which in the above case would be something like:

	reveal.js/plugin/highlight/highlight.js

The regex will thus give out 'reveal.js' as a file depency instead of the
expected 'highlight.js'

The fix is quiet easy: simply make sure that we are looking for a file that
actually ends with '.js' instead of simply containing '.js' by adding a $.

its->it's in README.md

Thanks for the multi-control support!

merge postmessage api

fix vertical transition for vertically centered slides, vertical centering is now on by default (#70)