Metric Monitoring: Set Prometheus Version Tag (#384)

* Allow port specification for Prometheus

* Add monitoring example with grafana

This commit adds an example in the example folder. It helps
the user to visualize clipper metric.

The init_grafana.py script launches a grafana/grafana docker
container. It adds prometheus as a data source. I attempted
to add the dashboard via Grafana API but failed after trying
it out for hours. This seems like a persistent issue for at
least two years: grafana/grafana#2816

<Simon Mo>

* Fix dict unpacking lint error

* Format Code

* Update yapf

* Update yapf and reformat code

* Check yapf version in shell script

* Change `echo` to `cat`

* Add python version check; almost ready

* Format code with python version 2.7.12

* Allow port specification for Prometheus

* Add monitoring example with grafana

This commit adds an example in the example folder. It helps
the user to visualize clipper metric.

The init_grafana.py script launches a grafana/grafana docker
container. It adds prometheus as a data source. I attempted
to add the dashboard via Grafana API but failed after trying
it out for hours. This seems like a persistent issue for at
least two years: grafana/grafana#2816

<Simon Mo>

* Update Metric Config; Finish Implement Model Container

* Add Integration Test

* Fix Integration Tests

* Format Code and Rebase from Develop

* Format Code Again with python2.7.12

* Update monitoring readme; trigger Jenkins

* Address Comments

1. Fix naming and typos
2. Update configuration buckets

* Format Code

* Address comments

- use 1000.0 instead 1000 rpc arithmatic.
- change docs

* Address RPC Test issue

Add a block of code make sure config file is found.

* Update tensowflowcifar

* [Metric] Update metrics example showing anomaly

* [Metric] Fix version tag for prometheus

* [Metric] Change version tag to master

* Format Code

* Change prom version fron master to v2.1.0

clipper_admin/clipper_admin/docker/docker_metric_utils.py

@@ -4,6 +4,8 @@
 import os
 from ..version import __version__
 
+PROM_VERSION = "v2.1.0"
+
 
 def ensure_clipper_tmp():
     """
@@ -98,7 +100,7 @@ def run_metric_image(docker_client, common_labels, prometheus_port,
     ]
     metric_labels = common_labels.copy()
     docker_client.containers.run(
-        "prom/prometheus",
+        "prom/prometheus:{}".format(PROM_VERSION),
         metric_cmd,
         name="metric_frontend-{}".format(random.randint(0, 100000)),
         ports={'9090/tcp': prometheus_port},