Merge branch 'fork-icon' into 'master'

New fork icon!

## What does this MR do?
We are using the old fork icon for branching only, so this implements our new custom fork icon

## Screenshots (if relevant)
![Screen_Shot_2016-07-15_at_9.22.33_AM](/uploads/05abaffff314e41f582189327bcca6b2/Screen_Shot_2016-07-15_at_9.22.33_AM.png)     
![Screen_Shot_2016-07-15_at_9.29.14_AM](/uploads/a08c622c92da00945406bbd4b3497749/Screen_Shot_2016-07-15_at_9.29.14_AM.png)

cc @hazelyang 

See merge request !5276

app/assets/stylesheets/framework/buttons.scss

@@ -49,6 +49,17 @@
     border-color: $border-dark;
     color: $color;
   }
+
+  svg {
+
+    path {
+      fill: $color;
+    }
+
+    use {
+      stroke: $color;
+    }
+  }
 }
 @mixin btn-green {
@@ -173,6 +184,13 @@
   .caret {
     margin-left: 5px;
   }
+
+  svg {
+    height: 15px;
+    width: auto;
+    position: relative;
+    top: 2px;
+  }
 }
 .btn-lg {

app/assets/stylesheets/pages/projects.scss

@@ -129,6 +129,17 @@
       color: $layout-link-gray;
     }
+    svg {
+
+      path {
+        fill: $layout-link-gray;
+      }
+
+      use {
+        stroke: $layout-link-gray;
+      }
+    }
+
     .fa-caret-down {
       margin-left: 3px;
     }

app/views/projects/buttons/_fork.html.haml

@@ -2,7 +2,7 @@
   - if current_user && can?(current_user, :fork_project, @project)
     - if current_user.already_forked?(@project) && current_user.manageable_namespaces.size < 2
       = link_to namespace_project_path(current_user, current_user.fork_of(@project)), title: 'Go to your fork', class: 'btn has-tooltip' do
-        = icon('code-fork fw')
+        = custom_icon('icon_fork')
         Fork
       %div.count-with-arrow
         %span.arrow
@@ -10,7 +10,7 @@
           = @project.forks_count
     - else
       = link_to new_namespace_project_fork_path(@project.namespace, @project), title: "Fork project", class: 'btn has-tooltip' do
-        = icon('code-fork fw')
+        = custom_icon('icon_fork')
         Fork
       %div.count-with-arrow
         %span.arrow

app/views/projects/forks/index.html.haml

@@ -31,11 +31,11 @@
     - if current_user && can?(current_user, :fork_project, @project)
       - if current_user.already_forked?(@project) && current_user.manageable_namespaces.size < 2
         = link_to namespace_project_path(current_user, current_user.fork_of(@project)), title: 'Go to your fork', class: 'btn btn-new' do
-          = icon('code-fork fw')
+          = custom_icon('icon_fork')
           Fork
       - else
         = link_to new_namespace_project_fork_path(@project.namespace, @project), title: "Fork project", class: 'btn btn-new' do
-          = icon('code-fork fw')
+          = custom_icon('icon_fork')
           Fork

app/views/shared/icons/_icon_fork.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="40" height="40" viewBox="0 0 40 40" xmlns:xlink="http://www.w3.org/1999/xlink"><defs><circle id="a" cx="4" cy="4" r="4"/><mask id="d" width="8" height="8" x="0" y="0" fill="#fff"><use xlink:href="#a"/></mask><circle id="b" cx="20" cy="4" r="4"/><mask id="e" width="8" height="8" x="0" y="0" fill="#fff"><use xlink:href="#b"/></mask><circle id="c" cx="12" cy="30" r="4"/><mask id="f" width="8" height="8" x="0" y="0" fill="#fff"><use xlink:href="#c"/></mask></defs><g fill="none" fill-rule="evenodd" transform="translate(8 3)"><path fill="#7E7E7E" d="M10 19.667c-4.14-1.29-7.389-5.878-7.389-5.878C2.274 13.353 2 12.545 2 12.01V6h4v5.509c0 .276.166.65.367.831 0 0 1.136 1.028 1.746 1.574C9.617 15.261 11.048 16 12.09 16c1.028 0 2.41-.723 3.858-2.048.588-.54 1.84-1.742 1.84-1.742a.784.784 0 0 0 .211-.502V6h4v6.008c0 .548-.259 1.349-.601 1.795 0 0-3.21 4.707-7.399 5.916V27h-4v-7.333z"/><use stroke="#7E7E7E" stroke-width="4" mask="url(#d)" xlink:href="#a"/><use stroke="#7E7E7E" stroke-width="4" mask="url(#e)" xlink:href="#b"/><use stroke="#7E7E7E" stroke-width="4" mask="url(#f)" xlink:href="#c"/></g></svg>
\ No newline at end of file