Handle being able to take transform args as an array with opts.

Transform arguments can be passed in as a string such as...
`transform: ['es6ify']`
or you can wrap it in an array and have the second item be an options hash...
`transform: ['reactify', ['es6ify, {"global": true}]]`
Merge pull request #153 from paperlesspost/transform_options

Handle being able to take transform args as an array with opts.