Sanitise tarballs in mirror client

Within mirror client, clean items outside main package directory from
tarballs before attempting to upload them. Some package tarballs have
extraneous stuff in them (pax_global_header files, MacOS hidden files,
etc.) that causes them to fail the "tarbomb" test in the server.
Fix #158: download counts go up and down

Display both "recent" (last 30 days) and "total" (all time) download
counts on package page.
Fix #177: implicitly redirect foo/reports to foo-latestversion/reports
Update HTTP to the latest version
Fix deleting maintainers, and possibly other actions using _method.

The authentication hash for digest authentication includes the method, but that might have been changed by methodOverrideHack. rqRealMethod tries to find out if this was the case, and if so, returns POST instead of rqMethod. But it does this by looking at the post data, and Happstack doesn't return post data for requests other than POST and PUT.

For maintainers deletion, _method was set to DELETE, so authentication failed and users were repeatedly presented with authentication dialogs. We now set the method to POST temporarily before checking if a _method parameter was present.

Fixes #197.
Make README useful

I'd really like to see the README contain useful information on how to
quickly get started with the hackage server. In this commit I started
with some of the info on the wiki page, and fixed/updated this info in
several cases. Some of the updates I made:

* Add travis-ci build status to README
* Update commands to use `cabal`
* Fix steps for mirroring since wiki seems to use outdated instructions

If we merge this, I'll also delete the outdated info on the
wiki. Thanks - let me know if you think anything else should be done
to merge this or if you disagree with the changes I made!
Merge pull request #200 from hesselink/fix-maintainer-deletion

Fix deleting maintainers, and possibly other actions using _method.
Merge pull request #194 from horus/HTTP_update

Update HTTP to the latest version
Merge pull request #193 from ian-ross/issue-177

Fix #177: implicitly redirect foo/reports to foo-latestversion/reports
Merge pull request #191 from ian-ross/issue-158

Fix #158: download counts go up and down
Merge pull request #190 from ian-ross/mirror-tarball-sanitisation

Sanitise tarballs in mirror client
Merge pull request #202 from jsl/readme_tweaks

Make README useful
Various tweaks to the README