When a user is not authorized to see the list of hooks for a project, he is
still able to access the hooks separately. For example if access to
`GET /projects/:id/hooks` fails and returns a `403 Unauthorized` error it is
still possible to access a hook directly via `GET /projects/:id/hooks/:hook_id`.

Fixes access, also added tests to check access and status codes of hooks.

When reaching the project limit the API returns an error code 404 on the last possible
project. The project itself is created and is available in the database (seems valid).
A similar behavior can be observed when reaching the project limit via web client, but
in this case the user is notified that the maximum number of projects is reached. The project
itself is still created and can be accessed.

Tests are added to check the behavior when reaching the project limit or one tries
to exceed it via the API.

Accessing a repository branch that does not exist returns a 404 error instead
of 200 now. Added a test.

Fixed mistake with updating project hook

Also (I think) I found few mistakes with snippets requests.

Merge branch 'master' into non-interactive-aws-install

Conflicts:
	doc/installation.md

Fix merge mess in installation.md

Changes:
* Move spec/monkeypatch to spec/support
* Remove unused support/shared_examples
* Move support/api to support/api_helpers to match module name
* Move support/login to support/login_helpers to match module name
* Move API specs to requests/api (convention over configuration)
* Remove unused support/js_patch
* Simplify login_as helper
* Move DatabaseCleaner stuff to its own support file
* Remove unnecessary configuration and requires from spec_helper

Didn't bother with files in db/, config/, or features/