The prefix is not reflected in the # HELP and # TYPE lines

[JDA88]

Describe the bug
When you use a prefix the # HELP and # TYPE lines in the generated metric file does not reflect it.
Effectively rendering those line inefectives

To Reproduce
Steps to reproduce the behavior:

1. Use prefix: aci_
2. Look at the generated files

# HELP health_ratio Returns health score
# TYPE health_ratio gauge
aci_health_ratio

Expected behavior
It should be:

# HELP aci_health_ratio Returns health score
# TYPE aci_health_ratio gauge
aci_health_ratio

[thenodon]

@JDA88 thanks for the issue report. This is fixed in branch issue_22 so it can be tested with issue #22.

[thenodon]

Merged in #27