Dcos-shakedown

Fixes:

- fix partitioning bug (QUALITY-1432), use new network APIs rather than
SSH-based command execution

Features:

- new security methods:
- `ensure_resource()`
- `add_user()`, `get_user()`, `remove_user()`
- `set_user_permission()`
- `add_group()`, `get_group()`, and `remove_group()`
- `add_user_to_group()`, `remove_user_from_group()`
- new security contexts:
- `credentials()`
- `no_user()`
- `new_dcos_user()`
- `dcos_user()`
- `wait_while_exceptions()` spinner
- new contexts available for Marathon-on-Marathon (MoM) deployments
- `mom_version()`
- `mom_version_less_than()`
- `marathon_on_marathon()`

Fixes:

- Shakedown now functions without authentication options on clusters not
requiring authentication

Features:

- `wait_for` waits for service endpoints to be debounced
successfully in a specified number of masters in multi-master
setups
- new PyTest decorators methods for determining Shakedown versions
- `shakedown_canonical_version()`
- `shakedown_version_less_than()`
- new methods for determining leaders in multi-master setups
- `marathon_leader_ip()`
- `master_leader_ip()`

Fixes:

- fixed lack zookeeper-related methods failing in methods running
commands on masters
- fixup for `kill_process_from_pid_file_on_host()` which only killed
processes on master

Features:

- ability to start a HTTP server running on the master via
`start_master_http_service()` method, along with an associated
`master_http_service()` context
- new methods for killing processes based on pidfiles
- `kill_process_from_pid_file_on_host()`
- `kill_process_from_pid_file_on_master()`

Fixes:

- include `partition_cmd` file in package distribution
- fixup for `test_install_package_with_subcommand` test
- corrected `dcos_agents_state()` example usage docs
- `wait_for` now aborts when encountering exception chains

Fixes:

- `private_agents()` and `public_agents()` bug in `1.3.0`