How to animate growth of a social network? I am seeking for a library/tool to visualize how social network changes when new nodes/edges are added to it.

One of the existing solutions is SoNIA: Social Network Image Animator. It let's you make movies like this one. 

SoNIA's documentation says that it's broken at the moment, and besides this I would prefer JavaScript-based solution instead. So, my question is: are you familiar with any tools or are you able to point me to some libraries which would make this task as easy as possible?

Right after posting this question I'll dig into sigma.js, so please consider this library covered.

In general, my input data would be something like this:

time_elapsed; node1; node2
1; A; B
2; A; C
3; B; C


So, here we have three points in time (1, 2, 3), three nodes (A, B, C), and three edges, which represent a triadic closure between the three considered nodes.

Moreover, every node will have two attributes (age and gender), so I would like to be able to change the shape/colour of the nodes.

Also, after adding a new node, it would be perfect to have some ForceAtlas2 or similar algorithm to adjust the layout of the graph.
Fancy animations are cool
I was very impressed when I saw this animation of the discourse git repository. They used Gourse which is specifically for git. But it may give ideas about how to represent the dynamics of growth.
You can create animations with matplotlib
This stackoverflow answer seems to point at a python/networkx/matplotlib solution.
But D3.js provides interaction
If you're looking for a web-based solution then d3.js is excellent. See this, this and this for example.
See also this stackoverflow question, the accepted answer points to D3.js again.
Conclusion
I would be drawn towards the python/networkx options for network analysis (possibly to add attributes to your raw data file for example). Then, for visualisation and dissemination D3.js is perfect. You might be surprised how easy it can be to write d3.js once you get into it. I believe it even works within an ipython notebook!