Clean up project.clj.

Relates to #113.

- remove undocumented :namespaces
- simple alias doesn't require vector
- order changed to the one used in the official documentation
- add url and license metadata
- build aborts on conflicting dependency versions
- uberjar profile fixes warning that main will be no longer included in
  aot by default with lein 3.x
Remove lein-ring plugin.

Fixes #113.

Because we provide our own main method the plugin is not longer used.
Fix offset on next link.

Fixes #120.

The next link now increases the offset by the amount of limit instead of
hardcoded 25.
Merge pull request #121 from mvitz/120-next-button-offset

Fix offset on next link.
Merge pull request #115 from mvitz/remove-lein-ring-plugin

Remove lein ring plugin.
Add tests for atom feeds.

Relates to #72.
Refactor atom feed generation.

Relates to #72.
Fix author uri for atom feed entries.

Relates to #72.
Date constructs in atom feed now contain ms.

Relates to #72.

As of http://tools.ietf.org/html/rfc4287#section-3.3 time should:
> Date values SHOULD be as accurate as possible. For example, it would
  be generally inappropriate for a publishing system to apply the same
  timestamp to several entries that were published during the course of
  a single day.
Fix feed author uri.

Relates to #72.
Fix atom feed self link.

Relates to #72.
Fix atom feed id.

Relates to #72.

__Note__: This fix is not backwards compatible as it changes the id for
each atom feed.
Add atom feed entry links to conversation and in-reply-to.

Fixes #72.

- link to html of entry has 'type=text/html' and 'rel=alternate'
- links to converation with 'rel=related'
- links to status it's a reply to with 'rel=prev'