fix missing Model issue when using items in operation

e.g.
@SWG\Operations(
  @SWG\Operation(
     method="GET",
     type="array",
     items="$ref:Pet"
  )
)
Added $swagger->examine($phpcode) to improve unittesting.
Accept comma-separated property names for @SWG\Model(required="id,name")

Both notations json and comma-separated are accepted:
required="['id','name']"
required="id, name"
Notify when @SWG\Property(required=true) is written as @SWG\Property(required="true")
@SWG\Model(required) is now also inherited. Fixes #116
Extract descriptions from the docblock.

Applies to @SWG\Model, @SWG\Resource, @SWG\Property and @SWG\Api
Build 0.8.2