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
Attempt to fix #9 & #13
fix a 404 in the readme - blog base url changed
Enable syntax highlighting for code snippets.
Merge branch 'johnjohndoe-patch-1' into dev
Merge branch 'ligi-fix_readme_404' into dev
Fix to comply with 0.10+ android gradle plugin.
Merge commit '44a1e74d01afd31ae1b78e6d85d1ab992295bb82' into dev