fix version + doc

additionals_fields.md

 ## Addtionals fields supported
 
-Using marshmallow schema, you can add some extra field in field who are
-automatically added into field description in schema.
+Using marshmallow schema, you have the possibility to add extra information in
+field in order to add them into auto-generated apispec documentation.
+
 ```
         class MySchema(marshmallow.Schema):
             category = marshmallow.fields.String(

hapic/__init__.py

 from hapic.data import HapicData
 from hapic.infos import __version__
 
-__version__ = '0.41'
 _hapic_default = Hapic()
 
 with_api_doc = _hapic_default.with_api_doc