docs(customizing_deis): remove slugbuilder/slugrunner settings

These were removed in a builder refactor and are no longer respected.
Merge pull request #2798 from carmstrong/builder_slugbuilder_docs

docs(customizing_deis): remove slugbuilder/slugrunner settings
chore(client+controller): update python requests lib to 2.5.1
Merge pull request #2796 from mboersma/update-py-requests

chore(client+controller): update python requests lib to 2.5.1