Don't inject kredits service in models

app/models/proposal.js

@@ -1,12 +1,8 @@
 import EmberObject from '@ember/object';
-import { computed } from '@ember/object';
 import { alias } from '@ember/object/computed';
-import { inject as injectService } from '@ember/service';
 import bignumber from 'kredits-web/utils/cps/bignumber';
 
 export default EmberObject.extend({
-  kredits: injectService(),
-
   // Contract
   id: bignumber('idRaw', 'toString'),
   creatorAccount: null,
@@ -26,10 +22,4 @@ export default EmberObject.extend({
   details: {},
   url: null,
   ipfsData: '',
-
-  // Relationships
-  // TODO: Optimize it. We don't need to find the contributor every time we add a new one
-  contributor: computed('contributorId', 'kredits.contributors.[]', function() {
-    return this.get('kredits.contributors').findBy('id', this.contributorId);
-  })
 });