Added WARCTap(WARC Scheme and WARCCollector) and a simple testcase.

1. Modified the gradle file to support dependencies too.
2. Created a new package `cascading.warc` and added a Tap and Scheme for supporting WARC file formats based on `com.martinkl.warc.mapred.WARC[Input,Output]Format`
3. Created a simple testcase for the new cascading tap.