Use concrete for uniform Makefile goodness
Add support for bracketed ipv6 address literals when generating URLs

The format_s3_uri helper function calls http_uri:parse/2 and we now
specify option {ipv6_host_with_brackets, true}. This gives us basic
support for ipv6 address literals.

Note that format_s3_uri supports both virtual host and path based
bucket syntax. For IP addresses, the virtual host option returns a
value, but one that won't work. If you're using IP addresses, you need
to stick to type 'path'.
Merge pull request #10 from opscode/sf/ipv6

Add support for bracketed ipv6 address literals when generating URLs