Forward {upload,receive}-pack requests to Gitaly

Closes gitaly#125

See merge request !143

Closes gitlab-org/gitaly#125

Pass full Gitaly 'Repository' message on from Rails

See merge request !147

We are in the middle of making the Gitaly 'Repository' message contain
more fields than it used to. This change makes sure that workhorse
automatically passes through the new message format (as long as the
gitaly client versions in gitlab-rails and workhorse match).

Version 1.4.2

See merge request !146

Return error 500, if possible, from GET /info/refs

Closes #121

See merge request !145

Update Redis references in README

See merge request !142

Version 1.4.1

See merge request !141

Redis fixes

Closes #117 and #114

See merge request !140

The redigomock package is GPLv2. Because I am unsure if this is
compatible with our own license and because we will have the GitLab
9.0 release soon I am adding this hack to keep redigomock in our test
suite but out of our sources.

Also: https://gitlab.com/gitlab-org/gitlab-workhorse/issues/114

Bug-fix for redis connection

See merge request !137

Fix for internal/redis.TestWatchKey{AlreadyChanged,MassiveParallel}

Closes #111

See merge request !136

Track errTooManyRequests in prometheus

Closes #106

See merge request !127

Don't log errors to Sentry.
Reduce helpers usage in favor of simple http error

Do not follow redirects when doing api calls.

Closes #107

See merge request !134

+ small code cleanup

Make redirects work in go < 1.7

Support v4 CI API

Closes #110

See merge request !133

Version 1.4.0

See merge request !139

Mark Redis experimental while we sort out bugs

See merge request !138