* Add qdisc collector for Linux
This collector gathers basic queueing discipline metrics via netlink,
similarly to what `tc -s qdisc show` does.
* qdisc collector: nl-specific code moved, names fixed
- netlink-specific parts moved to github.com/ema/qdisc
- avoid using shortened names
- counters renamed into XXX_total
* Get rid of parseMessage error checking leftover
* Add github.com/ema/qdisc to vendored packages
* Update help texts and comments
* Add qdisc collector to README file
* qdisc collector end-to-end testing
* Update qdisc dependency to latest version
Update github.com/ema/qdisc dependency to revision 2c7e72d, which
includes unit testing.
* qdisc collector: rename "iface" label into "device"
Emanuele Rocca