Improve relative URL support

This also removes the -relativeURLRoot setting introduced in 0.5.0.

See merge request !19

The missing trailing / on example.com/gitlab was making us throw a
404.

Make GitLab Workhorse passthrough to Unicorn

It works :)


See merge request !12

Use Go 1.5.2 for tests



See merge request !15

Make error style more uniform

Deprecate 'logContext' in favor of just passing Go error values.

Also adds to missing 'return' statements after a 'fail500' in archive.go.

See merge request !16