Updated to Dropwizard 0.5.1

Includes rename of `artifactId` for `dropwizard-extra-scala_2.9.1` to
`dropwizard-extra-scala`.
Clean up management of common dependencies

We now use a `<dependencyManagement>` section in the parent POM to
set the versions of common dependencies (e.g. test deps and upstream
Dropwizard deps).
Add Scala sources to source JAR

In order to meet the requirements for Maven central, all modules must
provide a source JAR.
Add GitHub Pages URL to POMs

The master site for the project and its sub-modules will be hosted as a
GitHub Pages site at: `http://datasift.github.com/dropwizard-extra`
Fix POM License to use plain text ASL 2.0

The HTML version breaks Maven generated documentation on License.
Fix Scala module name

We can't use properties in the `project.name` without things breaking.
Manage plugins with pluginManagement

Also removes the unused `wagon-ssh` dependency from the
`maven-deploy-plugin` as we were never using it.
Link Javadoc to external sources

Links the following Javadoc sources to the generated Javadoc:

  * [Dropwizard](http://dropwizard.codahale.com/)
  * [Metrics](http://metrics.codahale.com/)
  * HBase's [asynchbase](http://github.com/stumbleupon/asynchbase)
  * StumbleUpon's [Async](http://github.com/stumbleupon/async) library
Fix dropwizard-extra-scala to not compile twice

We were compiling the Scala sources twice to ensure that they're
compiled when any Java sources get compiled. This is unnecessary, as the
Scala module is not a mixed project.
Fix site generation for Scala module

We need to use the old-style `<reporting>` block for plugin config
inheritence for now.
Add markdown support to generated site

Markdown is better, so lets use it for our site templates. Also attaches
site descriptor to main artifact explicitly.
Add support for publishing site to GitHub Pages

Site is published by invoking the `site-deploy` goal explicitly, or by
making a release using the `maven-release-plugin`.
Add Sonatype OSS parent for publishing to Central

The Sonatype OSS parent POM handles releases using the
`maven-release-plugin`, providing a release profile:
`sonatype-oss-release`, which (by default):

  * Attaches source JAR (using the `maven-source-plugin`)
  * Attaches docs JAR (using the `maven-javadoc-plugin`)
  * Signs artifacts using GPG key (using the `maven-gpg-plugin`)

The `dropwizard-extra-scala` module explicitly overrides the profile to
add it's sources to the `maven-source-plugin` and produce an attached
docs JAR.
Minor tweaks to some ScalaDoc
Add an initial site descriptor

This is a first stab at producing a useful site for Dropwizard Extra
using the `maven-site-plugin`.
Fix aggregation of docs by parent POM

The generated site contained an aggregated set of docs for all modules
in the root of the project.

It featured broken links to dependencies and gave the erroneous
impression that classes from adjacent modules were related.

This also disables the generation of test docs, as tests are not a part
of the public API.
Fix missing version from reporting plugins

We must define the version of all reporting plugins because they ignore
`pluginManagement`.
Add outputEncoding to POM

Everything should be UTF-8 for portability.
Define developer roles

I'm the `architect` and principal `developer`, so lets make a note of
that.
Remove github plugin

We can't portably deploy a site to GitHub Pages using their plugin, so
lets remove it.

Ideally, we should be able to just use Maven's native Git support and
just override the branch to `gh-pages`. Unfortunately, you can't
override the branch in the POM at the moment.

For now, lets disable deployment of the site by commenting out the URL.