Update observers.md

Right now I'm learning Ember and I found this example a litle bit hard to crack. If my understanding of Ember observers is correct they will only fire if the property is "consumed". In this Example this is not the case and therefore fullnameChanged is not executed. If readers without much knowledge of the underlying concepts try this out it simply won't work.
Consume observer with .on('init')
Add the Brussels Meetup Group.
Merge pull request #1021 from YoranBrondsema/master

Add the Brussels Meetup group
Merge pull request #1020 from Mythli/patch-1

Is it required to consume the observer in the first example?
Update to Ember 1.1.1.
Merge pull request #1023 from rjackson/update_ember_version

Update to Ember 1.1.1.
Update docs for 1.1.1.
Fix starter-kit URL.
invalid json, missing comma
Merge pull request #1024 from amirdt22/json-typo

invalid json, missing comma
Improve readability.
Merge pull request #1025 from ugisozols/readability

Improve readability.
Fixing documenation for rending into

The code looks for the route based on the into property, not the
template
Merge pull request #1026 from kingpin2k/master

Fixing documenation for rending into
Ember 1.1.1/1.2 beta blog post
Update displaying-the-number-of-incomplete-todos.md

The code on this page will not run unless there is a comma after the definition of 'inflection'. It is possible that this was truncated on purpose, in which case please disregard.
Merge pull request #1029 from taidan19/patch-1

Update displaying-the-number-of-incomplete-todos.md