Allow lazy fragment initializaiton through promise

[vigneshshanmugam]

• This is a backward compatible change

fixes #92

[grassator]

I would restructure this to have something like:

function doInit(init, callback) {
// do actual initialization and when done do callback
}
doInit(init, measureInitCost.bind(null, fragmentId, 'fragment-');

That way you can avoid multiple early returns.

[grassator]

I think that init function should rather return a promise

[dazld]

pull this out into a library function and import it

[vigneshshanmugam]

I would keep it simple.. will probably even inline it than keeping it as fn

[dazld]

maybe, but it's probably something that should be covered by a test, so pulling it out into a library func is going to help with that.

[vigneshshanmugam]

Yeah i didnt do that since its not used anywhere other than this one place..

[dazld]

oki