Fix command splitting and joining when an argument contains spaces

[emillynge]

At the moment ECS and compose transformers performs a "dumb" argument splitting.

This means that the following compose entrypoint:

entrypoint: ['/bin/echo', 'Hello world']

gets incorrectly transformed into /bin/echo hello world which fails as echo only expects 1 argument.

conversely ECS emits '/bin/echo "Hello world" as

"entryPoint": [
               "/bin/echo",
               "\"Hello",
               "world\""
           ]

This PR fixes these and adds tests for the failure mode.

[coveralls]

Changes Unknown when pulling be510cc on emillynge:shlex_splitting into ** on micahhausler:master**.

[micahhausler]

@emillynge thanks for making this! Any chance you could squash the 3 commits down to one?

[coveralls]

Changes Unknown when pulling 0cd967e on emillynge:shlex_splitting into ** on micahhausler:master**.

[emillynge]

I would, but it seems like a hassle that is unnecessary since this is actually built-in as a tool for the maintainer.

Squash to only one “proper” commit for github pull request

Note that Bob doesn't have to squash his commits when he is making a GitHub PR.
Since March 2016, you can leave that operation to the maintainer (you) accepting your PR.

The thread refers to this post Squash your commits

[emillynge]

By the way, I have expanded the code change to the kubernetes, marathon and chronos module as well for consistency.
I don't use these, so please check that I haven't fucked something up.

Also I have changed the "unsplitting" slightly as I found out that shlex.quote() is a bit agressive (quoting stuff that did not need escaping).
Now I use shlex.split to check whether quoting is necessary for each item in a list of commands. To have this, slightly more complex, code declared only once, I have taken the liberty of adding a static method ._list2cmdline(commands: list) -> str to the Transformer base class. (I couldn't find any utils module)

[coveralls]

Changes Unknown when pulling 472f9b6 on emillynge:shlex_splitting into ** on micahhausler:master**.

[emillynge]

Found the time to squash to just 1 commit. :)

Should be ready to merge without further ado

[emillynge]

I'm thinking @micahhausler maybe didn't get a notification :)

Everything should be ready to merge.

[micahhausler]

Thanks @emillynge !