Support for setting root element
Added support for :only and :except methods.

It is possible now to filter returned attributes and associations by:

  UserSerializer.new(user, only: [:first_name, :last_name])
  UserSerializer.new(user, except: :first_name)
Update README.md

Fixed typo in documentation about the number of options to disable the root element for arrays
Merge pull request #291 from silviorelli/patch-1

Update README.md [ci skip]
include serializer support into mongoid
Merge pull request #292 from goshakkk/patch-1

include serializer support into mongoid
allow singular embed when serializing association

Having

```ruby
has_one :post, embed: :ids
```

looks especially weird as it's a one-to-one association, hence there is
only one id. The following looks better:

```ruby
has_one :post, embed: :id
```
add support of mongoid collection serialization
Merge pull request #294 from goshakkk/has-one

allow singular embed when serializing association
Merge pull request #293 from goshakkk/mongoid-support

add support of mongoid collection serialization
Merge pull request #283 from morgoth/add-only-and-except-options-support

Add only and except options support
Merge pull request #264 from vad4msiu/features/root_element

Support for setting root element
Add CodeClimate badge.
Update CHANGELOG for 0.8.0
Add Coveralls for code coverage.
Bump to 0.8.0
allow serializers to implement an options attribute
Merge pull request #295 from SamSaffron/master

Allow serializers to implement options
CHANGELOG for 0.8.1
version bump 0.8.1