Use Go 1.5.3



See merge request !33

Add DESTDIR support to "make install"

Fixes https://gitlab.com/gitlab-org/gitlab-workhorse/issues/8

See merge request !27

Use gitlab-zip-cat to send zip entries

Fixes https://gitlab.com/gitlab-org/gitlab-workhorse/issues/17

See merge request !31

Configure URLPrefix before building routes

Fixes #19 

See merge request !32

Add support for new artifacts features

It is proof of concept implementation that misses following:

- [x] Saving metadata to file, and passing that file to rails,
- [x] Making it look nice,
- [x] Have `refactor-upstream` merged: https://gitlab.com/gitlab-org/gitlab-workhorse/merge_requests/20
- [x] Add tests for metadata and single file downloads,
- [ ] Spawning separate process to verify zip archive **ONHOLD**: https://gitlab.com/gitlab-org/gitlab-workhorse/issues/17,
- [ ] Spawning separate process to download file from zip archive **ONHOLD**: https://gitlab.com/gitlab-org/gitlab-workhorse/issues/17


See merge request !28

This test duplicates some of what is in internal/artifacts but
@grzesiek and I felt it was important to have an integration test that
also covers the route to this resource.

Uses escaper from mime/multipart/writer.go.

* commit '3bbb1be7':
  Version 0.6.0
  Gotta commit those moved files
  Develomentmode ended up the wrong way around
  Move test helpers into seperate package
  Prevent package testing from going into the build

Develomentmode ended up the wrong way around



See merge request !29