Moving the global muting logic to a shared helper method
A few changes to the global muting logic to match code style
No longer require the sprite parameter in the play method when just passing a callback function
Deprecate fadeIn and fadeOut and add a more robust fade method
Small tweak to the doc comments
Update minified file and bump to v1.1.6
Hotfix for a missing parameter that somehow missed the 1.1.6 commit in global muting
Make `node.play` async when not using webAudio

It took me half day to figure out why Howler is not working in the latest Firefox release. If I manually load the `.ogg` file in the browser, Howler.play works beautifully but if the file is not loaded, there was no sound coming out. 

By wrapping the `node.play` in a `setTimeout(func, 0)` wrapper, we force the `play` event to wait till the current loading event is finished. 

Please note that Firefox's default setting for `media.webaudio.enabled` is `false`, which is why `self._webAudio` code path wasn't selected.
Make url's method work again and allow a string to be passed as the parameter if only one URL is being passed
Merge pull request #62 from alexdong/master

Make `node.play` async when not using webAudio
Merge branch 'master' of https://github.com/goldfire/howler.js
Generated new minified version and bump to v1.1.8
Changing volume before sound has loaded now has desired effect (v1.1.9).