If upgrading from a version of node_exporter <0.15.0 you'll need to update any
custom command line flags that you may have set as it now requires a
double-dash (--flag) instead of a single dash (-flag).
The collector flags in 0.15.0 have now been replaced with individual boolean
flags and the -collector.procfs` and -collector.sysfs` flags have been renamed
to --path.procfs and --path.sysfs respectively.