Caching the contents of jar file on disk turned on by default. Significant speed improvement.
Add assemblyCacheUnzip key to allow disabling of cached output. Change mappings to keep track of their parent jars where applicable. Compute the sha1 hash of the jar rather than extracted class files when deciding whether to rebuild when cacheOutput is set. Significant speedups.
Added some documentation, and a test for unzip caching behaviour to ensure that a jar built before and after caching has the same content hash.
Merge pull request #83 from d40cht/master

Caching the contents of jars on disk from run-to-run