Fix highlighting of current user in contributor list

Fixes #72

Introduces a helper to determine if a contributor is the current user.

app/components/contributor-list/template.hbs

@@ -1,6 +1,6 @@
 <tbody>
   {{#each contributors as |contributor|}}
-    <tr role="button" class={{if contributor.isCurrentUser "current-user"}} {{action "toggleContributorInfo" contributor}}>
+    <tr role="button" class={{if (is-current-user contributor) "current-user"}} {{action "toggleContributorInfo" contributor}}>
       <td class="person">
         <img class="avatar" src={{contributor.avatarURL}} alt="">
         {{contributor.name}}
@@ -10,7 +10,7 @@
         <span class="symbol">₭S</span>
       </td>
     </tr>
-    <tr class="metadata {{if contributor.isCurrentUser "current-user"}} {{if contributor.showMetadata "visible"}}">
+    <tr class="metadata {{if (is-current-user contributor) "current-user"}} {{if contributor.showMetadata "visible"}}">
       <td colspan="2">
         <ul>
           <li><a href="https://testnet.etherscan.io/address/{{contributor.account}}">Inspect Ethereum transactions</a></li>

app/helpers/is-current-user.js

@@ -0,0 +1,16 @@
+import Helper from '@ember/component/helper';
+import { inject as service } from '@ember/service';
+import { alias } from '@ember/object/computed';
+import { isPresent } from '@ember/utils';
+
+export default Helper.extend({
+
+  kredits: service(),
+  currentUser: alias('kredits.currentUser'),
+
+  compute([contributor]) {
+    return isPresent(contributor) && isPresent(this.currentUser) &&
+            contributor.account === this.currentUser.account;
+  }
+
+});

app/models/contributor.js

@@ -19,9 +19,6 @@ export default EmberObject.extend({
   wiki_username: null,
   ipfsData: '',
 
-  // Deprecated
-  isCurrentUser: false,
-
   avatarURL: computed('github_uid', function() {
     let github_uid = this.github_uid;
     if (github_uid) {