ref(builder): remove dockerfile from builder
fix(docs): move subheaders down a level for correct nav

The "PR Checklist" doc had all its subheaders at the same level as
the main header (h1 instead of h2), causing them to show up in the
right column navigation links.
ref(deisctl): stop/uninstall store in order
docs(managing_deis): always stop platform before uninstalling
docs(managing_deis): add workaround for store component failures
Merge pull request #2296 from mboersma/fix-contrib-headers

fix(docs): move subheaders down a level for correct nav
docs(install_deisctl): import shield badges
Revert "fix(docs): turn off "warnings as errors" for sphinx-build"

This reverts commit ad1c1cd0e61dac6cbdacf50c318f1a14242f7e47.
fix(deisctl): start gateway before volume
Merge pull request #2310 from bacongobbler/import-images-docs

docs(install_deisctl): import shield badges
docs(README): remove deprecated clusters troubleshooting
Merge pull request #2314 from bacongobbler/remove-clusters-from-reaadme

docs(README): remove deprecated clusters troubleshooting
chore(client): update requests to 2.4.3
chore(builder): update requests to 2.4.3
Merge pull request #2307 from carmstrong/deisctl_wait_on_stop

fix(deisctl): use wait groups for stopping and uninstalling store
Merge pull request #2263 from aledbf/remove_dockerfile_from_builder

ref(builder): remove dockerfile parser from builder
Merge pull request #2315 from mboersma/update-python-requests

chore(*): update python requests to 2.4.3
fix(*): etcd_set_default and etcd_safe_mkdir raise some errors

Currently, both `etcd_set_default` and `etcd_safe_mkdir` in
the /bin/boot scripts never fail due to `|| true`. This is usually
desired because if the key already exists, we don't want to overwrite
it. However, if there is an underlying error connecting to etcd, we
swallow that as well.

This commit exploits the fact that `etcdctl` has different exit codes
for key errors and etcd errors to swallow only the errors we wish to.