Add openmetrics python parser to integration tests

[hollodotme]

Expected Behavior

All produces metrics must be able to be parsed by the openmetrics python parser.

Actual Behavior

Metrics are only tested via unit tests.

Specifications

• Package version: v0.2.0
• PHP version: 7.2

Further comments

The following script is able to parse a file that contains exposed metrics.

Install prometheus_client and forked-path:

pip install prometheus_client forked-path

parseFile.py:

from prometheus_client.openmetrics.parser import text_string_to_metric_families
from path import path

metrics = path('/path/to/metrics.txt').bytes()

for family in text_string_to_metric_families(metrics):
  for sample in family.samples:
    print("Name: {0} Labels: {1} Value: {2} Timestamp: {3}".format(*sample))