Add minitest to Gemfile. Fix #3826

There are occasions where minitest is not bundled in packaged
versions of ruby that some OSes distribute (eg Fedora). Adding
minitest to Gemfile ensures that it gets loaded and tests can run.
Signed-off-by: Axilleas Pipinellis <axilleas@archlinux.gr>

fix API route to delete project hook

Fixed forgotten unicorn to puma in a comment.

link contribution guide to test section in README

Create DeployKey & DeployKeysProject models. Bulding many to many relation between deploy keys and projects

Changed forgotten unicorn to puma in the init script

Remove 2000 char limit on issue description

fork failing when calling initialize_dup

initialize_dup has been made private as of ruby 2.0.0. I have
corrected it to call the publicly available dup method

fix ace editor Syntax Highlighter mode load 404

add proper code/command formatting where missing in CONTRIBUTING.md

link to RSpec. related to #3810

link to spinach in the README. Closes #3810

Internally public projects

updated fork feature to use gitlab-shell for v5 of gitlab