add VMware Fusion support

[zaps]

This is a small modification to the che.sh startup script that adds an optional --vmware flag to have docker-machine use the vmwarefusion driver instead of the virtualbox driver, for those users that don't have or want to install VirtualBox.

[TylerJewell]

@zaps CLA looks good.
Let's go ahead and change this to --machine:fusion and --machine:vbox as the configured option with vbox as the default for mac / windows. We will then accept it.

[zaps]

Will do.
I noticed there already is a --machine switch for specifying the name of the machine so right now, running for example che.sh --machine:vbox will create a docker-machine with name 'vbox'.

Instead, could we add another option, maybe --machine-driver to specify the driver type?
I.e. --machine-driver:fusion. If the option is not given it would default to vbox.

Otherwise, we'd have to do something like --machine:name=myCheMachine,driver=fusion. And again if the argument isn't provided it would default to default/vbox.

[TylerJewell]

Ahhh didn't notice that --machine was already used. Yes --machine-driver:vbox and --machine-driver:fusion is better approach.

[zaps]

ok all set!

[TylerJewell]

Looks good to me. Past all my tests. Congrats on the first merge.