Disk utilisation plugin.

Returns metrics for all devices listed by iostat that do not start with
'dm-'. The metric is the %util over a period of 5 seconds from when the
check is run.
updates for 10.0.0
Merge pull request #103 from git-harry/cdm

Disk utilisation plugin.
Merge pull request #108 from mancdaz/10.0.0

updates for 10.0.0
Change uint32 ms types to double

We are dealing w/ floats here so the metric type needs to be updated
accordingly.

Closes #106