#171 create UnnecessaryAnonymousRunnable rule

[Hamlet D'Arcy]

create UnnecessaryAnonymousRunnable rule

There is no need to create an anonymous inner class of type Runnable. Just use a closure instead.
We should scan for all other one method interfaces within the JDK as well.

[Chris Mair]

The inner class name is not available in the AST in Groovy 1.7, but is available in 1.8. Once we can standardize on Groovy 1.8+, we can implement a rule that checks for the predefined set of one-method interfaces in the JDK.