Make CI Lint form synchronous

This removes `remote: true` from CI Lint form, making it synchronous
form. This also removes some complexity related to displaying lint
messages.

View also has been updated, removed deprecated Bootstrap 2 tags.
Improved design.

Closes #4206

app/controllers/ci/lints_controller.rb

@@ -19,8 +19,10 @@ module Ci
       @error = e.message
       @status = false
     rescue
-      @error = "Undefined error"
+      @error = 'Undefined error'
       @status = false
+    ensure
+      render :show
     end
   end
 end

app/views/ci/lints/_create.html.haml

@@ -41,5 +41,3 @@
     %i.fa.fa-remove.incorrect-syntax
   %b Error:
   = @error
-
-    

app/views/ci/lints/create.js.haml

-:plain
-  $(".results").html("#{escape_javascript(render "create")}")
\ No newline at end of file

app/views/ci/lints/show.html.haml

 %h2 Check your .gitlab-ci.yml
 %hr
-= form_tag ci_lint_path, method: :post, remote: true do
-  .control-group
-    = label_tag :content, "Content of .gitlab-ci.yml", class: 'control-label'
-    .controls
-      = text_area_tag :content, nil, class: 'form-control span1', rows: 7, require: true
-  .control-group.clearfix
-    .controls.pull-left.prepend-top-10
-      = submit_tag "Validate", class: 'btn btn-success submit-yml'
-
-
-%p.text-center.loading
-  %i.fa.fa-refresh.fa-spin
-
-.results.prepend-top-20
-
-:javascript
-  $(".loading").hide();
-  $('form').bind('ajax:beforeSend', function() {
-    $(".loading").show();
-  });
-  $('form').bind('ajax:complete', function() {
-    $(".loading").hide();
-  });
+.row
+  = form_tag ci_lint_path, method: :post do
+    .form-group
+      = label_tag :content, 'Content of .gitlab-ci.yml', class: 'control-label text-nowrap'
+      .col-sm-12
+        = text_area_tag :content, nil, class: 'form-control span1', rows: 7, require: true
+    .col-sm-12
+      .pull-left.prepend-top-10
+        = submit_tag 'Validate', class: 'btn btn-success submit-yml'
+.row.prepend-top-20
+  .col-sm-12
+    .results
+      = render partial: 'create' if defined?(@status)

spec/features/ci_lint_spec.rb

@@ -5,7 +5,7 @@ describe 'CI Lint' do
     login_as :user
   end
-  describe 'YAML parsing', js: true do
+  describe 'YAML parsing' do
     before do
       visit ci_lint_path
       fill_in 'content', with: yaml_content