Added HelloWorld sample (copied from wiki)

The wiki ( https://github.com/box/box-java-sdk-v2/wiki/HelloWorld )
already has a sample app.  Checking that app into the SDK itself,
along with an Ant build.xml file to make it super easy to use.
Convert tabs to spaces in sample code
Fix sample code for deleting a file

Sample code for deleting a file was boxClient.deleteFile(...); should be boxClient.getFilesManager().deleteFile(...).
Merge pull request #22 from mmorearty/hello-world-sample

Added HelloWorld sample (copied from wiki)
Merge pull request #23 from mmorearty/patch-1

Fix sample code for deleting a file