Ignore failed deletions in ObjectPersister

This probably isn't the best way to solve my problem,
but the issue is this.

Step 1:  Create a new doctrine entity for which it's `is_indexable_callback`
returns false.  When doctrine flushes this entity to the database,
elastia will not index it with elastic search.  (Correct)

Step 2:  Update your doctrine entity and change some fields so
that `is_indexable_callback` _still_ returns false.  Persist and flush
to the database.

At this point, the postUpdate listener on ElastiaBundle is called
and since the `is_indexable_callback` returns false, it believes
it needs to remove it from the elastic search index and queues it
for deletion.  The deletion of course fails because it was never there
in the first place.

This solution simply ignores failures from deletions in the index.

Perhaps a better solution would be to have a smarter listener
that could determine if the entity was previously present in the
elastic search index or not, but that would require significant
refactoring.

Addresses issues discuseed in #284

Credit to @bbeaulant for simple solution.  Opening a PR to
discuss more generally.
Document object mapping implications for Doctrine ORM
Merge pull request #316
Update README.md
Merge pull request #318 from RobertPlant/patch-1

Update README.md
Fix output colors
An orderBy DQL  part is required to avoid feching the same row twice
Allow elastica 0.90. Elasticsearch made the jump from 0.20 to 0.90
Merge pull request #326 from Tobion/patch-1

Allow elastica 0.90. Elasticsearch made the jump from 0.20 to 0.90
Merge pull request #321 from ajgarlag/fix-output-color

Fix output colors for single type commands
Removes sort call
Remove unused parameter from ModelToElasticaAutoTransformer.php
Merge pull request #330 from tgabi333/patch-1

Remove unused parameter from ModelToElasticaAutoTransformer.php
Merge pull request #323 from ajgarlag/orm-provider-order-by

An orderBy DQL  part is required to avoid feching the same row twice
Fix missing getter for private field test for PropertyAccess 2.3+

See: https://github.com/symfony/PropertyAccess/commit/df67239b02a9cef12cf84579f6cf569680298238
Add filtered query example to README.md
Rewrite filtered query example in README

Cleaning up the description paragraph and removing extra fields and pagination from the example, since we already have pagination examples elsewhere in the README.
Merge pull request #338 from FriendsOfSymfony/2.0.x-property-access

Fix missing getter for private field test for PropertyAccess 2.3+
Merge branch '2.0.x' into 2.1.x

Conflicts:
	Tests/Transformer/ModelToElasticaAutoTransformerTest.php
Fix expected exception class (related to #338)

This corrects a typo in a66a37aebd7424e9a82e81bd1a3760abb735ea7e.