Modern Linux has a lots of boring filesystem (tmpfs on /dev, devpts on
/dev/pts, lots of cgroup on /sys/fs/cgroup/*, ...).
* Ignore filesystem with 0 bytes (this cover cgroup, devpts and other).
* Add IgnoreFS to ignore additional FS by their type. Add tmpfs and
devtmpfs as default ignored type.
This will basically make the root directory a place for storing the
major telegraf interfaces, which will make telegraf's godoc looks quite
a bit nicer. And make it easier for contributors to lookup the few data
types that they actually care about.
closes#564