Consider dropping support for v0.8 metrics

[pilhuhn]

Hawkular Metrics is in both OpenShift and H-Services way beyond version 0.8
I expect that there are no more installations of H-Metrics 0.8 out there.
We should remove support for it completely from the gem

CC @simon3z

[abonas]

@pilhuhn what parts of the client in particular are specific to supporting 0.8?
regardless I +1 this

[josejulio]

I think that there is only old cassettes that support the 0.8API and this check that supports versions below 0.16.

[pilhuhn]

Well, metrics_api checks on this in a few places like:

https://github.com/hawkular/hawkular-client-ruby/blob/master/lib/hawkular/metrics/metric_api.rb#L59

[simon3z]

As far as I know currently OpenShift is using these versions:

OpenShift Version	Hawkular Version
OpenShift 3.1	0.8.0
OpenShift 3.2	0.8.2
OpenShift 3.3	0.18.5
...	...

@mwringe please keep me honest on these.

@pilhuhn for CM OpenShift 3.2 went out of the ManageIQ matrix since Jan 2017 but it seems a little early to drop the support.

When are you planning this cleanup?
(Anyway we have to be careful with gems dependencies and possible backports because we don't want this cleanup to reach older versions of ManageIQ).

[pilhuhn]

@simon3z I haven't planned any concrete date. More a suggestion or thought so that we don't carry this around forever.
With the speed that OpenShift is progressing, I think that everyone will be on 3.3+ pretty soon