0.9/unipackage support

wanted to use this in my Cordova project, so whipped up the necessary changes to package.js :smiley_cat: 
imho its cleaner to do:
`api.export && api.export('');`

checking if === undefined is not always safe - in this case if most correct would be `if (typeof api.export == 'function')`

These notes go for versionsFrom too :)