Dependency between androidJavadocsJar and androidJavadocs

So that when you use the uploadArchives task, the Javadocs gets generated
Merge pull request #8 from MagicMicky/master

Dependency between androidJavadocsJar and androidJavadocs
Removed redundancy while setting vars

The README had most of the steps right, but it assumed that you set
the variables "group" and "version" in your build.gradle.  I've set
it up now so that this isn't necessary; you can just use VERSION_NAME
and GROUP without the middle man.

- Use "VERSION_NAME" instead of "version" for checking snapshot status

- Explicitly set groupId/version from GROUP and VERSION_NAME instead
  of assuming that group/version has been set previously.
Merge pull request #11 from dlew/vars

Removed redundancy while setting vars
Fixed link for blog post
Added signing info to readme

While not strictly necessary for uploads, it is needed if you're
closing a release on sonatype, so this seems like good advice to put
here.
Merge pull request #12 from dlew/readme

Updated README