SlidingMenu into Maven central

To make it easier to start using SlidingMenu it would be great if it was available through Maven central. Any users using Maven can add SlidingMenu to their project using a couple of lines of XML. Any users of the new Android build system by Google can also easily pull artifacts from Maven central.

The way for open source projects to get into Maven Central is by being synced from the Sonatype OSS repository. This involves GPG signing the artifacts and uploading the artifacts. It is appropriate for the project owner (@jfeinstein10) to do this himself. What needs to be done is detailed at https://docs.sonatype.org/display/Repository/Sonatype+OSS+Maven+Repository+Usage+Guide

This pull request prepares for this by adhering to the requirements of the Sonatype OSS repository.

Some notes:

* Needs Jeremy's email in the parent pom.
* Changed the groupId of the project because Jeremy does not own slidingmenu.com
* Made sure the build attaches source and javadoc jars
* Removed maps support because you cannot refer to the maps.jar since it is not present in Maven central.
* Reordered pom.xml elements according to http://maven.apache.org/developers/conventions/code.html

I hope this makes it a bit easier for Jeremy to get SlidingMenu into central.