Extract serializer logic into lib

To use the same code in hubot I extracted the serializer logic into lib to later move it into `truffle-kredits` when we are done with all other common logic.

app/models/contributor.js

@@ -1,14 +1,7 @@
-import Ember from 'ember';
 import computed from 'ember-computed';
-import injectService from 'ember-service/inject';
-
-const {
-  isPresent,
-} = Ember;
-
-export default Ember.Object.extend({
-  ipfs: injectService(),
+import EmberObject from 'ember-object';
 
+export default EmberObject.extend({
   id: null,
   address: null,
   name: null,
@@ -28,99 +21,4 @@ export default Ember.Object.extend({
       return `https://avatars2.githubusercontent.com/u/${github_uid}?v=3&s=128`;
     }
   }),
-
-  /**
-   * Loads the contributor's profile data from IPFS and sets local instance
-   * properties from it
-   *
-   * @method
-   * @public
-   */
-  loadProfile() {
-    let profileHash = this.get('profileHash');
-    if (!profileHash) {
-      return;
-    }
-
-    return this.get('ipfs')
-      .getFile(profileHash)
-      .then((content) => {
-        let profile = Ember.Object.create(JSON.parse(content));
-        this.set('ipfsData', JSON.stringify(profile, null, 2));
-
-        Ember.Logger.debug('[contributor] loaded contributor profile', profile);
-
-        this.setProperties({
-          name: profile.get('name'),
-          kind: profile.get('kind')
-        });
-
-        let accounts = profile.get('accounts');
-        let github   = accounts.findBy('site', 'github.com');
-        let wiki     = accounts.findBy('site', 'wiki.kosmos.org');
-
-        if (isPresent(github)) {
-          this.setProperties({
-            github_username: github.username,
-            github_uid: github.uid,
-          });
-        }
-        if (isPresent(wiki)) {
-          this.setProperties({
-            wiki_username: wiki.username
-          });
-        }
-      }).catch((err) => {
-        Ember.Logger.error('[contributor] error trying to load contributor profile', profileHash, err);
-      });
-  },
-
-  /**
-   * Creates a JSON-LD object of the contributor, according to
-   * https://github.com/67P/kosmos-schemas/blob/master/schemas/contributor.json
-   *
-   * @method
-   * @public
-   */
-  toJSON() {
-    let contributor = {
-      "@context": "https://schema.kosmos.org",
-      "@type": "Contributor",
-      "kind": this.get('kind'),
-      "name": this.get('name'),
-      "accounts": []
-    };
-
-    if (Ember.isPresent(this.get('url'))) {
-      contributor["url"] = this.get('url');
-    }
-    if (Ember.isPresent(this.get('github_uid'))) {
-      contributor.accounts.push({
-        "site": "github.com",
-        "uid": this.get('github_uid'),
-        "username": this.get('github_username'),
-        "url": `https://github.com/${this.get('github_username')}`
-      });
-    }
-    if (Ember.isPresent(this.get('wiki_username'))) {
-      contributor.accounts.push({
-        "site": "wiki.kosmos.org",
-        "username": this.get('wiki_username'),
-        "url": `https://wiki.kosmos.org/User:${this.get('wiki_username')}`
-      });
-    }
-
-    return contributor;
-  },
-
-  /**
-   * Returns the JSON-LD representation of the model as a string
-   *
-   * @method
-   * @public
-   */
-  serialize() {
-    return JSON.stringify(this.toJSON());
-  }
-
 });