Merge pull request #26 from raoulcjohnson/develop

PigModelExec: added target field
code clean up
code cleanup
Merge pull request #27 from xxdev/develop

Code clean up
update shifu-plugin-pig so it will build for either Hadoop 0.20 or
Hadoop 2.4 automatically. Will also automatically delete the results
folder when running. Code exists to prompt user, but is commented out.