Make client auto choose prediction endpoint

[milesgranger]

Will close #400

Problem

We use to have to manually specify prediction_path to Client for either /prediction or /anomaly/prediction

Solution

Now that we are returning 422 status code if the model being served is not an AnomalyDetector, the client can default to /anomaly/prediction and when it gets a 422 can update its prediction_path to /prediction instead for all future requests.

[codecov]

Codecov Report

Merging #425 into master will decrease coverage by 0.27%.
The diff coverage is 52.63%.

@@            Coverage Diff             @@
##           master     #425      +/-   ##
==========================================
- Coverage   89.23%   88.96%   -0.28%     
==========================================
  Files          52       52              
  Lines        2332     2347      +15     
==========================================
+ Hits         2081     2088       +7     
- Misses        251      259       +8

Impacted Files	Coverage Δ
gordo_components/client/io.py	77.41% <40%> (-4.07%)	⬇️
gordo_components/client/client.py	82.27% <57.14%> (-2.76%)	⬇️

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[epa095]

LGTM, but remember to change commit message!
And then you are allowed to use your mighty admin privileges to ignore the test-checks.