Consider a move to gradle?

Hi Saleem,

Attempting to run `ant` on a freshly-cloned copy of your project, I got this error:
```shell
BUILD FAILED
~/development/opensource/GenericObserver/build.xml:183: /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home does not exist.
```
I looked to fix this briefly, but then figured it'd take just as long to get a simple gradle file together. I wondered if you might consider a move to gradle for the project? 

I included a build file that runs all the tests with the same library versions as the lib directory with `gradle test` and generates intellij project files with `gradle idea`.

Let me know what you think :)