Support Decimal type in JSON serializer

SQLa Numeric types get returned as decimal.Decimal
objects. simplejson has support for this, whereas
the builtin json module does not and there's no clean
way to subclass it in a way that it won't convert
the value to a JSON string.

Fixes ColtonProvias#23

.gitignore

@@ -72,3 +72,6 @@ target/
 pyvenv.cfg
 pip-selfcheck.json
 
+# PyCharm
+.idea
+

requirements.txt

@@ -9,3 +9,4 @@ passlib==1.6.5
 pathtools==0.1.2
 SQLAlchemy-Utils==0.30.16
 pytest==2.7.3
+simplejson==3.8.2

sqlalchemy_jsonapi/flaskext.py

@@ -6,7 +6,7 @@
 """
 
 import datetime
-import json
+import simplejson as json
 import uuid
 from functools import wraps
 
@@ -35,6 +35,7 @@ def default(self, value):
             return str(value)
         return json.JSONEncoder.default(self, value)
 
+
 #: The views to generate
 views = [
     (Method.GET, Endpoint.COLLECTION), (Method.GET, Endpoint.RESOURCE),
@@ -235,7 +236,7 @@ def new_view(**kwargs):
                 response = override(exc, results)
             rendered_response = make_response('')
             if response.status_code != 204:
-                data = json.dumps(response.data, cls=self.json_encoder)
+                data = json.dumps(response.data, cls=self.json_encoder, use_decimal=True)
                 rendered_response = make_response(data)
             rendered_response.status_code = response.status_code
             rendered_response.content_type = 'application/vnd.api+json'