replace font-awesome gem. Use fork icon

Gemfile

@@ -129,7 +129,7 @@ group :assets do
   gem "modernizr",        "2.6.2"
   gem "raphael-rails",    git: "https://github.com/gitlabhq/raphael-rails.git"
   gem 'bootstrap-sass'
-  gem "font-awesome-sass-rails", "~> 3.0.0"
+  gem "font-awesome-rails", "~> 3.1.1"
   gem "gemoji", "~> 1.2.1", require: 'emoji/railtie'
   gem "gon"
 end

Gemfile.lock

@@ -130,9 +130,8 @@ GEM
       eventmachine (>= 0.12.0)
     ffaker (1.16.0)
     ffi (1.8.1)
-    font-awesome-sass-rails (3.0.2.2)
-      railties (>= 3.1.1)
-      sass-rails (>= 3.1.1)
+    font-awesome-rails (3.1.1.3)
+      railties (>= 3.2, < 5.0)
     foreman (0.63.0)
       dotenv (>= 0.7)
       thor (>= 0.13.6)
@@ -535,7 +534,7 @@ DEPENDENCIES
   enumerize
   factory_girl_rails
   ffaker
-  font-awesome-sass-rails (~> 3.0.0)
+  font-awesome-rails (~> 3.1.1)
   foreman
   gemoji (~> 1.2.1)
   github-linguist

app/views/projects/_clone_panel.html.haml

@@ -7,11 +7,12 @@
         - unless @project.empty_repo?
           - if can?(current_user, :fork_project, @project) && @project.namespace != current_user.namespace
             - if current_user.already_forked?(@project)
-              = link_to project_path(current_user.fork_of(@project)), class: 'btn grouped btn-primary' do
+              = link_to project_path(current_user.fork_of(@project)), class: 'btn grouped disabled' do
+                %i.icon-code-fork
                 Forked
             - else
               = link_to fork_project_path(@project), title: "Fork", class: "btn grouped", method: "POST" do
-                %i.icon-copy
+                %i.icon-code-fork
                 Fork
           - if can? current_user, :download_code, @project
             = link_to archive_project_repository_path(@project), class: "btn grouped" do