fix(client): return non-zero on errors

Some commands were inconsistent and returned 0 when an error
occurred. This makes the client more consistent with errors.

closes #767
refactor(client): remove provider functions

Deis no longer handles provider code, so these functions should not
exist in the client.
feat(client): add auth command

It's handy to have a `deis help auth` command which will show off the
documentation for the auth commands available to the user.
chore(controller): remove unused gevent package
refactor(systemd): clean up paths

harcoded paths are not required in shell environments. I've also
removed unnecessary uses of /bin/sh when we only require an
environment variable, since systemd can reference environment
variables through ${}.

ref: http://www.freedesktop.org/software/systemd/man/systemd.service.html#ExecStart=
docs(vagrant): update references to vagrant files

We hadn't updated the "provision a controller" document after moving
vagrant support out of contrib/.

Fixes #906.
docs(contributing): add TESTING footer

This message footer is strictly to help maintainers with testing
fixes made in the code base. Developers are directed to put any
instructions on how to test their changes here in the message body
such that maintainers can reference the TESTING section of the commit
for quality analysis.
chore(controller): install new pip 1.5.5

https://github.com/pypa/pip/compare/1.5.4...1.5.5
Merge pull request #912 from deis/add-testing-footer

docs(contributing): add TESTING footer
fix(readme): unify language with deis.io
Merge pull request #929 from deis/update-readme

fix(readme): unify language with deis.io
fix(Makefile): fix 'check-fleet' rule for $FLEETCTL_TUNNEL with port.
Merge pull request #905 from deis/remove-gevent

chore(controller): remove unused gevent package
fix(controller): restore App.destroy() and call delete()

The change in https://github.com/deis/deis/pull/839 didn't account
for Django REST framework methods that indirectly call delete().

Fixes #927.
Merge pull request #907 from deis/install-new-pip

chore(controller): install new pip 1.5.5
Merge pull request #930 from jperville/fleetctl-version-check-with-port

fix(Makefile): fix 'check-fleet' rule for $FLEETCTL_TUNNEL with explicit port.
fix(logger): allow digits in app name when parsing log file

Fixes #909.
Merge pull request #888 from deis/systemd-refactor

refactor(systemd): clean up paths
Merge pull request #898 from deis/client-cleanup

refactor(client): client cleanup; return non-zero on errors
Merge pull request #935 from deis/app-name-regexes

fix(logger): allow digits in app name when parsing log file