Added documentation page on local testing

[axsaucedo]

Added documentation page on local testing and fixed some other pieces on the docs.

Also added a link ot the python module from the Getting Started index for easier access as right now it's hard to find given it's only accessible through teh python wrapper section.

[seldondev]

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[seldondev]

Mon Mar 23 17:20:49 UTC 2020
The logs for [lint] [2] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-1586/2.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-1586 --build=2

[seldondev]

Mon Mar 23 17:21:03 UTC 2020
The logs for [pr-build] [1] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-1586/1.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-1586 --build=1

[axsaucedo]

/approve