Added User API and serializer

InvenTree/users/serializers.py

@@ -0,0 +1,15 @@
+from rest_framework import serializers
+from django.contrib.auth.models import User
+
+
+class UserSerializer(serializers.HyperlinkedModelSerializer):
+    """ Serializer for a User
+    """
+
+    class Meta:
+        model = User
+        fields = ('username',
+                  'first_name',
+                  'last_name',
+                  'email',)
+