Closes gitaly#199

It was only available for test and development environments and we need
it to run the `rake gettext:pack` command in omnibus which doesn't have
the test/dev gems installed.

This gem prevents Mash from responding to :permitted?, disabling mass
assignment protection for the Grape API

Closes gitaly#173

The idea is that after each feature spec example, we block all incoming
requests at the Rack level, go to the 'about:blank' page, and wait until
the current requests reach 0.

This should solve the problem where a request would end after database
cleaner performed the database truncation. The problem was that a GET
request can still lead to records creation (e.g. namespaces or routes).
Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Adds suppport for HTML 5 details and summary tags (https://github.com/vmg/redcarpet/issues/578)