Bug Fix for Safari: 
In safari when one hover a node, the caption text was not displayed
because one use .html() function to add text into svg text node.
In safari, we can't add html into svg text node. 

So I replace the .html() call by a .text() call and it work just fine
for all browsers. We just can't add formatting to the caption text with
this method.
Bug fix : EdgeClick function 

2 bugs appears with the conf.edgeClick function.

1) when defining a function in configuration, this function was never
called
2) when called (with bugfix), the clicked edge was not passed in
parameter.

I replace the code with a new one very similar to the nodeClick
function. This last one works fine so I use the same pattern and it
works fine as well for edge clicking now.
Merge pull request #408 from seb-doncker/master

replacement of #404 in the release-0.2.2 branch