Merge branch 'improve_button_styles' into 'master'

Improve button styles

I noticed a couple of buttons don't match the newer styles.

## Issue edit note form

### Current (cancel button is big)

![Screen_Shot_2016-01-08_at_2.18.29_PM](/uploads/c7928e6644e886090f55cb61076c9e89/Screen_Shot_2016-01-08_at_2.18.29_PM.png)

### Now

![Screen_Shot_2016-01-08_at_2.18.22_PM](/uploads/d15c3c458a08ce5a59c367c7fb379c31/Screen_Shot_2016-01-08_at_2.18.22_PM.png)

## Merge request code discussion

### Current

![Screen_Shot_2016-01-08_at_2.21.37_PM](/uploads/b970ff3e5d9ef5e62f83bb56d5505f8d/Screen_Shot_2016-01-08_at_2.21.37_PM.png)

### Now (Also changed to `btn-save` class which changes to green. This matches everything else)

![Screen_Shot_2016-01-08_at_2.22.01_PM](/uploads/ed520de72177de92efe21d236bb04d24/Screen_Shot_2016-01-08_at_2.22.01_PM.png)

cc/ @jschatz1 @skyruler @creamzy 

See merge request !2350

app/helpers/notes_helper.rb

@@ -67,7 +67,7 @@ module NotesHelper
       line_type:     line_type
     }
 
-    button_tag class: 'btn reply-btn js-discussion-reply-button',
+    button_tag class: 'btn btn-nr reply-btn js-discussion-reply-button',
                data: data, title: 'Add a reply' do
       link_text = icon('comment')
       link_text << ' Reply'

app/views/projects/notes/_edit_form.html.haml

@@ -6,5 +6,5 @@
       = render 'projects/notes/hints'
 
     .note-form-actions
-      = f.submit 'Save Comment', class: 'btn btn-primary btn-save btn-grouped js-comment-button'
-      = link_to  'Cancel', '#', class: 'btn btn-cancel note-edit-cancel'
+      = f.submit 'Save Comment', class: 'btn btn-nr btn-save btn-grouped js-comment-button'
+      = link_to  'Cancel', '#', class: 'btn btn-nr btn-cancel note-edit-cancel'

app/views/projects/notes/_form.html.haml

@@ -15,4 +15,4 @@
   .note-form-actions.clearfix
     = f.submit 'Add Comment', class: "btn btn-nr btn-create comment-btn btn-grouped js-comment-button"
     = yield(:note_actions)
-    %a.btn.btn-cancel.js-close-discussion-note-form Cancel
+    %a.btn.btn-nr.btn-cancel.js-close-discussion-note-form Cancel