Favlink 모델에 full-text 검색 기능추가

attr_searchable 젬을 이용하여 Favlink 모델에 Full-text 검색 기능을 추가함.

in Gemfile
```
gem 'attr_searchable'
```

in Favlink.rb
```
  include AttrSearchable

  attr_searchable :title, :description
  attr_searchable :bundlelink => "bundlelink.title"
```

in favlinks_controller.rb
```
-    @favlinks = @bundlelink ? @bundlelink.favlinks : (params[:whose] ? Favlink.whose(current_user) : Favlink.shared)
+    if params[:search]
+      @favlinks = Favlink.search(params[:search])
+    else
+      @favlinks = @bundlelink ? @bundlelink.favlinks : (params[:whose] ? Favlink.whose(current_user) : Favlink.shared)
+    end
```

in _sidebar.html.erb
```
    <form class="navbar-form navbar-right" style="margin-bottom:1.5em;">
       <div class="input-group">
           <input type="Search" name="search" placeholder="Search..." class="form-control" value="<%= params[:search] %>" />
           <div class="input-group-btn">
               <button class="btn btn-info">
               <span class="glyphicon glyphicon-search"></span>
               </button>
           </div>
       </div>
    </form>
```