Caching and performance improvements..

[ghost]

Basically cache alot of things and generate statistics for nodes.json every time data is transmitted. Then we use a .map() to generate the nodes.json (basically add flags), which woult be a hell lot faster than a forEach.
The graph will be a bit more complicated, but it can be a minute outdated, so we can simply regenerate the graph every minute. Also we should have one cache for all output formats.
A bit OT: Is there a way to do gzip? My servers do this via an nginx rev-proxy, but built-in support would be nice.

[tantive]

As zlib is already used in hopglass-server:
https://nodejs.org/api/zlib.html#zlib_examples