Browse hosts for .rrd files, call info. Add unit tests.

* Add unit tests sample data. 
* Add mocha to run unit tests, and rewire to test private methods.
* Implemented browsing collectd data directory for host information, 
and calling 'info' on each rrd path. 
* Next TODO: parse rrdtool info results (may be use node_rrd again?)
* Next TODO: expose 'info' as a REST method.
Merge branch 'master' of https://github.com/dzimine/collectd3
Add heatmap mock data