Add `rss` to the list of reserved post titles/slugs.

closes #1880
- added `rss` to core/server/models `generateSlug` reserved keywords
- added integration test for safe slug generation to core/test/integration/model/model_posts_spec.js
Fix hanging loading bar on deleting a post

Closes #1869

- Added an additional event listener for destroy event, then a listener
on the model for the sync event to finish the progress bar loader
Update placeholder of published data in editor

fixes #1351

- when a post has a published_at value show a blank
placeholder

- when a post doesn’t have a published_at
value then show the required published at value
format
Merge pull request #1885 from nicovalencia/issue-1880

Add `rss` to the list of reserved post titles/slugs.
Merge pull request #1886 from jgable/progressBarOnDelete

Fix hanging loading bar on deleting a post
Add bug report template link to CONTRIBUTING.md

There is now a GitHub link you can use to create a bug with the template.
Merge pull request #1888 from hswolff/additional-ux

Update placeholder of published data in editor
Shims for deleted (refactored away) files

closes #1873.
During file system merge upgrades of new releases, old files are not removed and node's require loads the old file instead of all the new ones in the new directory. The files in this commit act as a delegate for all other dependent scripts. These shim files explicitly require the new index.js.