Update Query Params guide to latest API iteration

See here for details, (don't don't merge this 
until that is merged):

https://github.com/emberjs/ember.js/pull/4468
Put builds app after common js, fix builds page
Merge pull request #1340 from mixonic/builds

Put builds app after common js, fix builds page
Change double quotes to single quotes.
Merge pull request #1343 from lxe/patch-1

Change double quotes to single quotes in an observer example.
Merge pull request #1336 from machty/new-qp-guides

Update Query Params guide to latest API iteration
Release 1.5.0-beta.4