There were several specs that were failing when run by themselves.

- Use the `helper` object, as per RSpec 3 standards
- Use `assign` to assign instance variables that helpers expect
- Add `StubConfiguration` support module

Just for consistency with our Capybara, DatabaseCleaner, WebMock, etc.
setups.

Reuse HTML Pipeline object in Markdown parser

The patches reduces pressure on GC and reduces markdown processing time

See merge request !905

The patches reduces pressure on GC and reduces markdown processing time

Added missing packages required by docker builds

This fixes backup failed tests, missing commands: `pg_dump` and `mysqldump`.

See merge request !889

Bump rugments to 1.0.0beta8 to fix C prototype function highlighting

Closes #1890

See merge request !902

update documentation styleguide

See merge request !904

Fix wrong order of issues when importing from github

### 1. What does this MR do?

The order of issues imported from GitHub is fixed.

### 2. Are there points in the code the reviewer needs to double check?

Nothing.

### 3. Why was this MR needed?

The default behaviors of GitHub API at listing issues are sort: :created and direction: :desc.

See GitHub API details at https://developer.github.com/v3/issues/#list-issues.

### 4. What are the relevant issue numbers / Feature requests?

Fixes #1791

### 5. Screenshots (if relevant)

Nothing

See merge request !898