commands: reorder posargs of `deploy`

The order is now "<target> <zapp>", which is consistent with the `swift
upload <container> <file>` in the `pyhton-swiftclient`.
tests: update expected deploy arg order
templates: rename zebra.js -> zerocloud.js
templates/index.html: s/zebra.js/zerocloud.js/
tests/test-bundle.t: s/zebra.js/zerocloud.js/
zpm: s/zebra.js/zerocloud.js/
zpm: abstract `_get_zerocloud_client`

This utility can be used elsewhere to handle the various auth args and
create a ZeroCloud client object.
tests/test_zpm: tests for _get_zerocloud_client
miniswift: add `download` method

This method can be used to download single files from a container,
similar to `swift download`.
Implement `zpm execute` command
tests: update cram tests to include `execute` cmd
Merge pull request #115 from larsbutler/zpm-execute

Add zpm execute command
Merge pull request #113 from larsbutler/rename-zebra-js

Rename zebra.js to zerocloud.js
doc: add execute command
doc: reorder commands

The commands are now ordered roughly in the order we expect users to
use them, i.e., with the important 'zpm new' first and the less
essential 'zpm version' last.
commands: refactor cmdline args for login

This gets rid of the duplication introduced in afe94a0716cd. We can
reuse this pattern for future groups of command line arguments.
commands: extract reusable pattern from login_args

We can now easily group other command line arguments in the future
without having to duplicate the logic.
Merge pull request #117 from mgeisler/execute

Improve handling of command line arg groups
Merge pull request #112 from larsbutler/reorder-deploy-args

Reorder deploy args (fixes #111)