Force the order of execution of JS using defer.

Force the order of execution of JS using defer.

- Defer allows the scripts to be downloaded async, however it *forces* the
browser to execute them in the order they appear in the DOM.
- There's a chance that we've had users hitting out of order execution between
this code causing Y.juju.App to not be defined during startTheApp. This should
force this to not occur.

- Testing this just isn't possible. We're not 100% sure that it's the issue
and it's darn unrepeatable. The only repeatable case was a stale cache.
However, it has been demonstrated on machines in incognito mode so there is
something there. It's just very hard to reproduce.

https://code.launchpad.net/~rharding/juju-gui/defer-all-the-things/+merge/176442

(do not edit description out of merge proposal)

[rharding, 2013-07-23 17:32:52]

Please take a look.

[gary.poster, 2013-07-23 17:42:57]

LGTM with discussion from IRC.  Namely, if we do this, please include a comment
about why--and about our concerns.  Might as well also mention the confusion
here (http://www.w3.org/TR/html5/scripting-1.html#attr-script-defer -- we should
not have defer or async on non-src script tags) vs your experience here
http://stevesouders.com/cuzillion/?c0=hj1hfft1_0_f&c1=hj1hfft3_1_f&c2=hj1hfft...

[jeff.pihach, 2013-07-23 17:56:57]

LGTM with Gary's comments

[rharding, 2013-07-23 17:59:02]

*** Submitted:

Force the order of execution of JS using defer.

- Defer allows the scripts to be downloaded async, however it *forces* the
browser to execute them in the order they appear in the DOM.
- There's a chance that we've had users hitting out of order execution between
this code causing Y.juju.App to not be defined during startTheApp. This should
force this to not occur.

- Testing this just isn't possible. We're not 100% sure that it's the issue
and it's darn unrepeatable. The only repeatable case was a stale cache.
However, it has been demonstrated on machines in incognito mode so there is
something there. It's just very hard to reproduce.

R=gary.poster
CC=
https://codereview.appspot.com/11571044