add minimum request threshold to PercentErrPerTimeFailureInterpreter

When configured, the interpreter will not trip if the number of requests in the window is below the threshold. The intention is to prevent the interpreter from tripping if the first request in a window is a failure.
Merge pull request #20 from mattnworb/percentage-threshold

add minimum request threshold to PercentErrPerTimeFailureInterpreter
Added "Retries Exceeded Callback"

When an intialization fails due to the max retries - we don't really tell the client anything. Add a callback to let them know that state has occurred.
Extensions to spring-batch's retry framework.

In particular, this adds the following capability:

1.  Support for the Callable class within the ExtendedRetryTemplate
2.  A Classifier instance which is based on guava predicates
3.  Some useful predicates
4.  A retry policy which is based on a generic exception classifier, rather than the existing SimpleRetryPolicy which assumes a Map based approach to determining exception classification.
Merge branch 'master' of github.com:mattinger/jrugged