Merge branch 'loic_movie' into 'master'

Added Loic's latest galaxy merger movie to the main page in the GEAR model section.

See merge request !12

data/astro.md

@@ -144,6 +144,9 @@ cooling and is one of the many models that are part of the [AGORA
 comparison
 project](http://adsabs.harvard.edu/abs/2014ApJS..210...14K).
 
+<div class="videowrapper"><iframe width="100%" height="100%" src="https://www.youtube.com/embed/2Afc6nBBFYw" frameborder="0" allowfullscreen></iframe>
+</div>
+
 ## Structure finder
 
 SWIFT can be linked to the VELOCIraptor phase-space structure finder