I'm just getting my feet wet with angular, but I found this great tutorial.
Here's a working plunk I put together with credit to Scott Allen and the above tutorial. Click search to display the sortable table.
For each column header you need to make it clickable - ng-click on a link will work. This will set the sortName of the column to sort.
<th>
<a href="#" ng-click="sortName='name'; sortReverse = !sortReverse">
<span ng-show="sortName == 'name' && sortReverse" class="glyphicon glyphicon-triangle-bottom"></span>
<span ng-show="sortName == 'name' && !sortReverse" class="glyphicon glyphicon-triangle-top"></span>
Name
</a>
</th>
Then, in the table body you can pipe in that sortName in the orderBy filter orderBy:sortName:sortReverse
<tr ng-repeat="repo in repos | orderBy:sortName:sortReverse | filter:searchRepos">
<td>{{repo.name}}</td>
<td class="tag tag-primary">{{repo.stargazers_count | number}}</td>
<td>{{repo.language}}</td>
</tr>