Added assertion for updateLink

Added an assertion for string type. Since you could also pass objects
to `updateLink` (which would always result in false in the next if
statement) containing a link. This PR notifies creators of serializers
so they always use a string when handling links.

Added test for links with type other than string
Removed a duplicate line.
Added test case for push link with null value
added failing test
updated test
made the test pass
added note about coalescing and custom URLs
Temporary fix for #2344 rollback after delete for recordArrays

This is a temporary fix, it's clear this code needs to be refactored.
Moreover I am not sure that removing deleted records from recordArrays
before they are deleted is a correct design decision.
Merge pull request #2371 from emberjs/fix_rollback_record_arrays

Temporary fix for #2344 rollback after delete for recordArrays
Merge pull request #2370 from H1D/coalescing_docs

added note about coalescing and custom URLs
Rollback after delete record failure

failing test for #2344
Merge pull request #2359 from sly7-7/rollback-after-save-error

Rollback after delete record failure
Add missing type information to the API docs.
update ember-local version
Merge pull request #2378 from bmac/api-type-info

Add missing type information to the API docs.
beta.11 changelog and package.json updates
Merge branch 'master' of github.com:emberjs/data
add beta.11 to ember addon
post-release version bump
[DOC] Fix typos in `ajaxSuccess`
Merge pull request #2382 from lsthornt/fix-ajaxSuccess-doc

[DOC] Fix typos in `ajaxSuccess`
[DOC] Update usage of AMS

`include` option is renamed as `embed_in_root`
in current stable version 0.9.
* https://github.com/rails-api/active_model_serializers/blob/0-9-stable/lib/active_model/serializer/association.rb#L11