sciirus: export elasticsearch to context
rules: add alerts timeline on index page

This patch adds a timeline with alerts count on the index page.
It is is using nvd3 (see http://nvd3.org/) to do the graph and
data are fetched in elasticsearch.
rules: improve timeline code

JS code has been moved in scirius.js file. The system now support
filtering by host. It also displays cumulative line if multiple
hosts are asked.

On low traffic box, the bar char was inconsistent and the plot is
now done with a line. This way we have a correct time axis.