Adding a CONTRIBUTING document

Adding a CONTRIBUTING document to take advantages of this:
https://github.com/blog/1184-contributing-guidelines
Fixes login issues with JS

When user entered wrong credentials a login screen still tried to fetch
allowed organizations. Also an error notification was not displayed.
965735 - Default System Custom Info : No error displayed on trying
to enter a duplicate keyname
Merge pull request #2348 from ares/bug/login_unauthenticated_requests

Fixes login issues with JS
require ruby193scl-wrapper-ruby

but rather using path, because the name of package can be changed in RHSCLv2
And yes, we actually do not use scl_rake in spec
965790 - Publish user admin flag
Merge pull request #2364 from komidore64/bug_965735

965735 - Default System Custom Info : No error displayed on trying to enter a duplicate keyname
properly recreating model index upon reindexing
Merge pull request #2375 from jlsherrill/reindex

properly recreating model index upon reindexing
Merge pull request #2372 from ares/bug/965790_admin_flag_propagation

965790 - Publish user admin flag
951228 - Systems Custom Information - Keyname and value needs to
enforce maximum length restrictions

951228 - tests for changes

951228 - fixing syntax error
change scl format to allow more commands under one scl session
Merge pull request #2363 from komidore64/bug_951228

951228 - Systems Custom Information - Keyname and value needs to enforce maximum length restrictions
Adding success notifications for creating and removing custom information keynames.
Merge pull request #2376 from omaciel/morenotifs

[FEEDBACK_PLEASE] Adds success notifs for creating and removing custom information keynames.
966708 - Menu: show manage orgs link without an org selected.
962484 - Manage Orgs: remove unnecessary require_org.
Merge pull request #2379 from waldenraines/966708-962484

Fix Manage org link not displayed and 403 if you don't have an organization selected
967943 - changeset apply - error if view publish/refresh in progress

This commit contains changes to raise an error if the user
attempts to apply (e.g promote) a changeset that contains
a content view that is currently being published or refreshed.
Merge pull request #2370 from xsuchy/pull-req-ruby193scl-wrapper-ruby3

require ruby193scl-wrapper-ruby